Merged gui.utils with gui.vbrowser.

Most gui.utils classes are vbrowser classes anyway.
Generic gui.utils will be moved out of vbrowser package.
Moved gui.util classs into vbrowser.
Moved VRSPresentation class to vlet vrs.
bugfix: when no tab is present: auto create new tab.
Added Virtual Root Proxy Node for hidden top level Root Nodes in
ResourceTree.
Added small Add and Delete icons to top Tab Panel Component.
Virtual Proxy (root) node must delegate canOpen and openLocation to
child ProxyNodes + ProxyFactories.
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