EZP-22321: Fix ezjscore cache not cleared on DFS

> **JIRA issue:** http://jira.ez.no/browse/EZP-22321
> **Alternative to** #893 

ezjscore cache with DFS isn't cleared correctly when cleared by id (ezjscore-packer). This is because the DFS implementation of `delete()` has never been recursive.

This fix adds a clear function (`ezjscCacheManager`) is added to the ezjscore cache item. It uses `deleteByDirList()` instead of `delete()` in order to recursively delete.