Refactor: Decouple cache change notifications from the real objects

[iJungleboy]

I'm submitting a

[x] feature request
[x] refactoring

...about

[x] caching / internals

Current Behavior / Expected Behavior

ATM the features notify the cache through a complex system of objects that it has changed.

We believe this is not the best architecture, and should simply revert to a key-based notification system.

Your environment

• 2sxc version(s): 17.09