As a first-time creator of the inspector plugin, it took
a while to actually understand exactly what's happening and
what's needed, so I've expanded with the information that I felt would
help make the tutorial easier for people doing their first foray into
making one of these plugins.
Tutorial for 3.2 suggests calling 'add_custom_property_editor' which is not a member of EditorInspectorPlugin; however 'add_property_editor' does exist.
