New reworked AnimatedSprite!

-New SpriteFrames editor, with support for drag&drop, multiple animation
sets, animation speed and loop.
-New AnimatedSprite, with support for all the new features!
AnimatedSprite3D has not been updated yet.
-Added support for drag&drop to other editors, such as resourcepreload,
sample library,  etc.

tools/editor/property_editor.cpp

@@ -2287,6 +2287,7 @@ bool PropertyEditor::_is_drop_valid(const Dictionary& p_drag_data, const Diction
 				}
 
 			}
+
 			if (drag_data.has("type") && String(drag_data["type"])=="files") {
 
 				Vector<String> files = drag_data["files"];