CMS-3765 Replace ExtJS grid - Try move the new TreeGrid to api.ui.treegrid

Moved `app.api.browse.treegrid` module to `api.ui.treegrid`
CMS-3765 Replace ExtJS grid - Try move the new TreeGrid to api.ui.treegrid

Updated interfaces and inheritance chain.
CMS-3765 Replace ExtJS grid - Try move the new TreeGrid to api.ui.treegrid

Removed api.node.Node
CMS-3765 Replace ExtJS grid - Try move the new TreeGrid to api.ui.treegrid

Updated treegrid module position.
Merge pull request #809 from enonic/CMS-3765

CMS-3765 Replace ExtJS grid - Try move the new TreeGrid to api.ui.treegrid