Batch of Bugfixes

-=-=-=-=-=-=-=-=-

-Fixed Export UV XForm (should work now). #923
-Fixed enforcement of limits in property editor. #919
-Fixed long-standing bug of export editings in script inheritance. #914, #859, #756
-Fixed horrible error reporting in shader language. #912
-Added kinematic collision with plane (please test well). #911
-Fixed double animation track insert when using 2D rigs. #904
-VKey updates offset parameter in sprite edition. #901
-Do not allow anymore a script to preload itself. (does not fix #899, but narrows it down)
-Avoid connection editor from overriding selected text. #897
-Fixed timer autostart. #876
-Fixed collision layers in 3D physics. #872
-Improved operators in shader #857
-Fixed ambient lighting bug #834
-Avoid editor from processing gamepad input #813
-Added not keyword #752

Please test!

tools/editor/animation_editor.cpp

@@ -2513,6 +2513,7 @@ void AnimationKeyEditor::_query_insert(const InsertData& p_id) {
 
 
 	if (insert_frame!=OS::get_singleton()->get_frames_drawn()) {
+		//clear insert list for the frame if frame changed
 		if (insert_confirm->is_visible())
 			return; //do nothing
 		insert_data.clear();
@@ -2520,6 +2521,12 @@ void AnimationKeyEditor::_query_insert(const InsertData& p_id) {
 	}
 	insert_frame=OS::get_singleton()->get_frames_drawn();
 
+	for (List<InsertData>::Element *E=insert_data.front();E;E=E->next()) {
+		//prevent insertion of multiple tracks
+		if (E->get().path==p_id.path)
+			return; //already inserted a track for this on this frame
+	}
+
 	insert_data.push_back(p_id);
 
 	if (p_id.track_idx==-1) {