The phpdoc for the sharing functions was very restrictive. As a
consequence passing node object (for example from the OCS Share API
where we don't really care if it is a file or folder), would actually
be invalid.
With this loser restriction the interfaces become more generic.
* sharedWith
* sharedBy
* shareOwner
Now all set/get strings with the id. (userId, groupId,
federatedsharerId).
This to avoid a huge amount of if statements
This allows all clients to quickly get the share info for a given path.
Instead of returning everything and filtering it then manually on the
client side.