CORE-5094 Fixes for caching root sub-folders.

DiskResourceServiceFacade#getSubFolders now accepts a Folder instead of just a path.
CORE-4374 Folder lazy-loading fix.

The TreeStore models somehow become out of sync between the TreeLoader and the TreeView's SelectionModel when calling TreeLoader#loadChildren in DiskResourcePresenterImpl#setSelectedFolderById.
Refreshing the folder with the DiskResourceView forces any children to be removed first, before loading them again from the service.