Allow configuring read cache settings

Looking at this, and keeping 📌 Document swapping out the client cache for increase performance Active in mind.

If we allow changing the cache time with the already (undocumented) ability to change the cache storage, the ability to manage cache is also necessary.

Adding Cache clearing support as part of Drupal Cache Clear, and via module config page.

Automatically closed - issue fixed for 2 weeks with no activity.