handle anonymous upload to reshared folder
fixing Notice: Undefined index: isPublic
on reshares we now recursively move to the root of all reshares - therefore some code has been refactured and added as a new public function
Merge branch 'master' into fixing-3942-master

Conflicts:
	apps/files/ajax/upload.php
removing unused getSharedItem()
fixing check if public share is a folder or not
Merge pull request #3946 from owncloud/fixing-3942-master

handle anonymous upload to reshared folder