From Valeriy Onuchin:

-  huge upgrade of guibuilder classes

   o improved robustness
   o improved simplicity in navigation and actions.
   o possibility to add and correctly edit complex widgets,
     e.g. TGTab
   o few actions added to guibuilder toolbar and menus.
   o property editor was redisigned.
   o possibility to place widgets with matrix layout added


git-svn-id: http://root.cern.ch/svn/root/trunk@14466 27541ba8-7e3a-0410-8455-c3a389f83636