Sounds better for me.

- some more code comments
- fixed bug in the expire function, cleanup all_versions array during run. Otherwise it could happen that we try to delete already deleted versions

some more clean-up, isVersioned() is no longer needed; rename hook fixed if a complete folder gets renamed

webdav returns "503 Service Unavailable" in case the ownCloud server is currently in maintenance mode.

This means that OC_Connector_Sabre_Client is no longer needed

 refs https://github.com/owncloud/core/commit/ae54364d7c8baf5138d166855db6431190963886

Fixing wrong documentation. Fixes https://github.com/owncloud/core/issues/1110 

adding file name checks and notifications to isFileNameValid() for . and empty file name