Proper `WebedOrm` representation
Turned `WebedCache` (including it's descendants `WebedMemcached` & `WebedRedis`) into "proper" Flask extensions, adhering to the proposed API with `init-app` etc.
Setup cache defaults
Fixed test cases which had started failing after updating `webed.ext.cache` extension
More succinct code thanks to `contextlib.contextmanager`
Fixed test cases
minor