CMS-3724 Replace ExtJS grid - Support for setting Nodes to be displayed

Updated TreeGridGuilder properties scope.
Added TreeNodeBuilder.
Removed redundant methods from TreeNode.
Added pinning to the TreeNode to be able to pin node to the root.
Merge pull request #820 from enonic/CMS-3724

CMS-3724 Replace ExtJS grid - Support for setting Nodes to be displayed