Allowed to set empty root collections as categories for easier display.
Merge branch 'public_collections'

Conflicts:
	CollectionTreePlugin.php
	controllers/IndexController.php
	models/Table/CollectionTree.php
	views/admin/plugins/collection-tree-config-form.php
	views/helpers/CollectionTreeFullList.php
Added an option to display only root collections in collections/browse page.
Merge branch 'collections_browse'

Conflicts:
	CollectionTreePlugin.php
	views/admin/plugins/collection-tree-config-form.php