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!

scene/main/timer.cpp

@@ -40,7 +40,8 @@ void Timer::_notification(int p_what) {
 #ifdef TOOLS_ENABLED
 				if (get_tree()->is_editor_hint() && get_tree()->get_edited_scene_root() && (get_tree()->get_edited_scene_root()==this || get_tree()->get_edited_scene_root()->is_a_parent_of(this)))
 					break;
-#endif				start();
+#endif
+				start();
 			}
 		} break;
 		case NOTIFICATION_PROCESS: {