Proofread and improve the whole class reference

- Document a few more properties and methods
- Add more information to many classes
- Fix lots of typos and gramar mistakes
- Use [code] tags for parameters consistently
- Use [b] and [i] tags consistently
- Put "Warning:" and "Note:" on their own line to be more visible,
  and make them always bold
- Tweak formatting in code examples to be more readable
- Use double quotes consistently
- Add more links to third-party technologies

doc/classes/EditorImportPlugin.xml

@@ -5,7 +5,7 @@
 	</brief_description>
 	<description>
 		EditorImportPlugins provide a way to extend the editor's resource import functionality. Use them to import resources from custom files or to provide alternatives to the editor's existing importers. Register your [EditorPlugin] with [method EditorPlugin.add_import_plugin].
-		EditorImportPlugins work by associating with specific file extensions and a resource type. See [method get_recognized_extensions] and [method get_resource_type]). They may optionally specify some import presets that affect the import process. EditorImportPlugins are responsible for creating the resources and saving them in the [code].import[/code] directory.
+		EditorImportPlugins work by associating with specific file extensions and a resource type. See [method get_recognized_extensions] and [method get_resource_type]. They may optionally specify some import presets that affect the import process. EditorImportPlugins are responsible for creating the resources and saving them in the [code].import[/code] directory.
 		Below is an example EditorImportPlugin that imports a [Mesh] from a file with the extension ".special" or ".spec":
 		[codeblock]
 		tool
@@ -41,7 +41,7 @@
 		        return FAILED
 
 		    var mesh = Mesh.new()
-		    # Fill the Mesh with data read in 'file', left as exercise to the reader
+		    # Fill the Mesh with data read in "file", left as an exercise to the reader
 
 		    var filename = save_path + "." + get_save_extension()
 		    ResourceSaver.save(filename, mesh)
@@ -58,21 +58,21 @@
 			<argument index="0" name="preset" type="int">
 			</argument>
 			<description>
-				Get the options and default values for the preset at this index. Returns an Array of Dictionaries with the following keys: [code]name[/code], [code]default_value[/code], [code]property_hint[/code] (optional), [code]hint_string[/code] (optional), [code]usage[/code] (optional).
+				Gets the options and default values for the preset at this index. Returns an Array of Dictionaries with the following keys: [code]name[/code], [code]default_value[/code], [code]property_hint[/code] (optional), [code]hint_string[/code] (optional), [code]usage[/code] (optional).
 			</description>
 		</method>
 		<method name="get_import_order" qualifiers="virtual">
 			<return type="int">
 			</return>
 			<description>
-				Get the order of this importer to be run when importing resources. Higher values will be called later. Use this to ensure the importer runs after the dependencies are already imported.
+				Gets the order of this importer to be run when importing resources. Higher values will be called later. Use this to ensure the importer runs after the dependencies are already imported.
 			</description>
 		</method>
 		<method name="get_importer_name" qualifiers="virtual">
 			<return type="String">
 			</return>
 			<description>
-				Get the unique name of the importer.
+				Gets the unique name of the importer.
 			</description>
 		</method>
 		<method name="get_option_visibility" qualifiers="virtual">
@@ -89,7 +89,7 @@
 			<return type="int">
 			</return>
 			<description>
-				Get the number of initial presets defined by the plugin. Use [method get_import_options] to get the default options for the preset and [method get_preset_name] to get the name of the preset.
+				Gets the number of initial presets defined by the plugin. Use [method get_import_options] to get the default options for the preset and [method get_preset_name] to get the name of the preset.
 			</description>
 		</method>
 		<method name="get_preset_name" qualifiers="virtual">
@@ -98,42 +98,42 @@
 			<argument index="0" name="preset" type="int">
 			</argument>
 			<description>
-				Get the name of the options preset at this index.
+				Gets the name of the options preset at this index.
 			</description>
 		</method>
 		<method name="get_priority" qualifiers="virtual">
 			<return type="float">
 			</return>
 			<description>
-				Get the priority of this plugin for the recognized extension. Higher priority plugins will be preferred. Default value is 1.0.
+				Gets the priority of this plugin for the recognized extension. Higher priority plugins will be preferred. Default value is 1.0.
 			</description>
 		</method>
 		<method name="get_recognized_extensions" qualifiers="virtual">
 			<return type="Array">
 			</return>
 			<description>
-				Get the list of file extensions to associate with this loader (case insensitive). e.g. [code]["obj"][/code].
+				Gets the list of file extensions to associate with this loader (case-insensitive). e.g. [code]["obj"][/code].
 			</description>
 		</method>
 		<method name="get_resource_type" qualifiers="virtual">
 			<return type="String">
 			</return>
 			<description>
-				Get the Godot resource type associated with this loader. e.g. [code]"Mesh"[/code] or [code]"Animation"[/code].
+				Gets the Godot resource type associated with this loader. e.g. [code]"Mesh"[/code] or [code]"Animation"[/code].
 			</description>
 		</method>
 		<method name="get_save_extension" qualifiers="virtual">
 			<return type="String">
 			</return>
 			<description>
-				Get the extension used to save this resource in the [code].import[/code] directory.
+				Gets the extension used to save this resource in the [code].import[/code] directory.
 			</description>
 		</method>
 		<method name="get_visible_name" qualifiers="virtual">
 			<return type="String">
 			</return>
 			<description>
-				Get the name to display in the import window.
+				Gets the name to display in the import window.
 			</description>
 		</method>
 		<method name="import" qualifiers="virtual">