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/editor_node.cpp

@@ -2819,6 +2819,8 @@ void EditorNode::animation_editor_make_visible(bool p_visible) {
 		//pd_anim->hide();
 		animation_editor->hide();
 //		scene_root_parent->set_margin(MARGIN_TOP,0);
+		if (!animation_vb->get_parent_control())
+			return;
 		animation_vb->get_parent_control()->minimum_size_changed();
 		top_split->set_collapsed(true);
 	}