Remove phpass and migrate to new Hasher interface

Remove phpass and migrate to new Hasher interface

This PR removes phpass and migrates to the new Hasher interface.

Please notice that due to https://github.com/owncloud/core/issues/10671 old hashes are not updated but the hashes are backwards compatible so this shouldn't hurt.
Once the sharing classes have a possibility to update the passwords of single shares those methods should be used within the newHash if block.