Hardware cursor implementation for Godot Engine 2.1

- Remove all references to the variable 'custom_mouse_cursor_hotspot' and 'custom_mouse_cursor' from the project settings.
- Indeed, to implement a custom cursor we need to define a sprite for each 'state' of the cursor. Using those variables in the projects settings would define only the _main_ cursor.
- Cleanup the VirtualServer (Remove references to cursor_set_visible, cursor_set_texture and cursor_set_pos)
- Cleanup the Input (set_mouse_in_window should not be used anymore)
- Update the documentation
- Implement it for windows, X11, Javascript, BB 10, OSx, iOS, server, android
- NOT IMPLEMENTED FOR WINRT (As of today, I'm not able to implement this one, this post might help)
- NOT IMPLEMENTED FOR HAIKU (Support of this platform seems perfunctory)
- Build it for Windows, Android and OSX

platform/android/os_android.cpp

@@ -142,7 +142,6 @@ void OS_Android::initialize(const VideoMode &p_desired, int p_video_driver, int
 		visual_server = memnew(VisualServerWrapMT(visual_server, false));
 	};
 	visual_server->init();
-	visual_server->cursor_set_visible(false, 0);
 
 	AudioDriverManagerSW::get_driver(p_audio_driver)->set_singleton();
 
@@ -325,6 +324,11 @@ void OS_Android::set_cursor_shape(CursorShape p_shape) {
 	//android really really really has no mouse.. how amazing..
 }
 
+void OS_Android::set_custom_mouse_cursor(const RES &p_cursor, CursorShape p_shape,  const Vector2 &p_hotspot) {
+
+	// Since android has no mouse, we do not need to change its texture (how amazing !)
+}
+
 void OS_Android::main_loop_begin() {
 
 	if (main_loop)