scrollbar, options and widgets changes

* complete scrollbar skin
* implement scrollbar functionality (scrolling with mouse)
* fix onMouseClick issues
* add tabs in options (graphics and general tab)
* add new option for limiting frame rate using scrollbar
* add new widget property "clipping" that will be used on scrollable areas

modules/core_styles/styles/tabbars.otui

@@ -1,4 +1,5 @@
 TabBar < UITabBar
+  size: 80 20
 TabBarPanel < Panel
 TabBarButton < UIButton
   size: 20 20
@@ -9,7 +10,6 @@ TabBarButton < UIButton
   icon-color: white
   color: #aaaaaa
   anchors.top: parent.top
-  margin-left: 5
   padding: 5
 
   $first:
@@ -17,6 +17,7 @@ TabBarButton < UIButton
 
   $!first:
     anchors.left: prev.right
+    margin-left: 5
 
   $hover !checked:
     image-clip: 0 20 20 20