post hook

* test case added to avoid adding them later

make sure that we don't try to access an already deleted files, fixes some file source not found warnings

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

fix missing dir creation for file versions (OC_Filesystemview::mkdir doesn't work here because it doesn't create directories recursively)

update routine implemented
version number of files_versions increased

Conflicts:

	apps/files_versions/lib/hooks.php

Part-ported filesystem operations to OC_FilesystemView
Refactored Storage class to depend on an OC_FsV object and have fewer static classes