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/plugins/sprite_frames_editor_plugin.h

@@ -36,6 +36,7 @@
 #include "scene/2d/animated_sprite.h"
 #include "scene/gui/file_dialog.h"
 #include "scene/gui/dialogs.h"
+#include "scene/gui/split_container.h"
 
 
 class SpriteFramesEditor : public PanelContainer {
@@ -49,10 +50,18 @@ class SpriteFramesEditor : public PanelContainer {
 	Button *empty2;
 	Button *move_up;
 	Button *move_down;
-	Tree *tree;
+	ItemList *tree;
 	bool loading_scene;
 	int sel;
 
+	HSplitContainer *split;
+	Button *new_anim;
+	Button *remove_anim;
+
+
+	Tree *animations;
+	SpinBox *anim_speed;
+	CheckButton *anim_loop;
 
 	EditorFileDialog *file;
 
@@ -60,10 +69,11 @@ class SpriteFramesEditor : public PanelContainer {
 
 	SpriteFrames *frames;
 
+	StringName edited_anim;
 
 	void _load_pressed();
 	void _load_scene_pressed();
-	void _file_load_request(const DVector<String>& p_path);
+	void _file_load_request(const DVector<String>& p_path, int p_at_pos=-1);
 	void _paste_pressed();
 	void _empty_pressed();
 	void _empty2_pressed();
@@ -71,11 +81,27 @@ class SpriteFramesEditor : public PanelContainer {
 	void _delete_confirm_pressed();
 	void _up_pressed();
 	void _down_pressed();
-	void _update_library();
+	void _update_library(bool p_skip_selector=false);
 	void _item_edited();
 
+
+
+	void _animation_select();
+	void _animation_name_edited();
+	void _animation_add();
+	void _animation_remove();
+	void _animation_loop_changed();
+	void _animation_fps_changed(double p_value);
+
+	bool updating;
+
 	UndoRedo *undo_redo;
 
+	bool _is_drop_valid(const Dictionary& p_drag_data, const Dictionary& p_item_data) const;
+	Variant get_drag_data_fw(const Point2& p_point,Control* p_from);
+	bool can_drop_data_fw(const Point2& p_point,const Variant& p_data,Control* p_from) const;
+	void drop_data_fw(const Point2& p_point,const Variant& p_data,Control* p_from);
+
 protected:
 	void _notification(int p_what);
 	void _input_event(InputEvent p_event);