CMS-4417 Content Manager - Delete action does not delete all the selected content

Fixed the selection usage. full selection should now ne used.
Fixed bug in `BrowseItemsSelectionPanel` when removing stashed selection
and only one non-stashed selection remained, that is displayed as
selectionItem.
Merge pull request #1051 from enonic/CMS-4417

CMS-4417 Content Manager - Delete action does not delete all the selecte...