EZP-22321: ezjscore cache id not cleared with dfs

http://jira.ez.no/browse/EZP-22321.

Fixed eZDFSFileHandler mysqli implementation of delete.

The interface states that directories are deleted, but the implementation only covered single files. It has been updated to delete a single file if there is one, and a set of files if there is none. Set of files can be deleted using name_trunk, if it applies, or using a wildcard if it doesn't.

A new name_trunk identifier has been added for ezjscore.