CMS-2180 Make ContentTreeGrid use new REST API for loading and searching content
CMS-2017 Ensure that ContentTreeGrid loads child content asynchronosly
CMS-2180 Make ContentTreeGrid use new REST API for loading and searching content
CMS-2017 Ensure that ContentTreeGrid loads child content asynchronosly

- merged with master
- removed remote sorting and old unused ext stores
- refactored FindContentRequest