2D editor GUI input rework. Changes are:

- The input handling is done into several distinct functions, and the
  code is more consistent.
- The actions' history is more precise ("Edited CanvasItem"
  is now "Rotated CanvasItem","Moved CanvasItem",etc...)
- Fixed a little bug about input key events not forwarded correctly to plugins
- IK is followed by default when you move a bone node, the alt-key allow
  you to move it normally

scene/2d/node_2d.cpp

@@ -46,10 +46,9 @@ Dictionary Node2D::_edit_get_state() const {
 }
 void Node2D::_edit_set_state(const Dictionary &p_state) {
 
-	Dictionary state = p_state;
-	pos = state["position"];
-	angle = state["rotation"];
-	_scale = state["scale"];
+	pos = p_state["position"];
+	angle = p_state["rotation"];
+	_scale = p_state["scale"];
 
 	_update_transform();
 	_change_notify("rotation");
@@ -60,6 +59,8 @@ void Node2D::_edit_set_state(const Dictionary &p_state) {
 
 void Node2D::_edit_set_position(const Point2 &p_position) {
 	pos = p_position;
+	_update_transform();
+	_change_notify("position");
 }
 
 Point2 Node2D::_edit_get_position() const {