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!

servers/visual/rasterizer.cpp

@@ -79,7 +79,7 @@ RID Rasterizer::_create_shader(const FixedMaterialShaderKey& p_key) {
 	if (texcoords_used&(1<<VS::FIXED_MATERIAL_TEXCOORD_UV_TRANSFORM)) {
 
 		code+="uniform mat4 fmp_uv_xform;\n";
-		code+="vec2 uv_xform = fmp_uv_xform * UV;\n";
+		code+="vec2 uv_xform = (fmp_uv_xform * vec4(UV,0,1)).xy;\n";
 	}
 
 	/* HANDLE NORMAL MAPPING */