As a developer, I'd like an overview of the cache contents

In the console I'd like to have an overview of caches and items per cache.

General idea:
* list view with all caches
* per entry the ability to purge
* detail view of a cache, listing the entries
* per entry the ability to purge
* per entry some datetime information (saved/expires?)

This ticket needs to be refined a bit more. Can be split on read only views and acionts