Implements #21

This is a breaking change.

Changelog:
- Redis is now mandatory and enabled by default
- Added Sentinel, Standalone and Cluster support
- Standalone mode with sidecar is used by default
  - If no host(s) are configured, a redis sidecar is injected into the deployment
  - No extra configuration needed
  - This is intended for development and does not scale.
- Helm values have changed, see README.md:
  - `redis.host` has been renamed to `redis.hosts` and expects a list of strings with the following pattern: <localhost:6379> (needed for sentinel and cluster modes)
  - `redis.port` has been removed, see `redis.hosts`

fix deployments that did not have this value configured at all
by providing a sensible default.

(see OXUI-1015)

during startup the ui-middleware might need some more memory, so we adjust the actual limit to something larger.

Fixes #6

since we don't expect admins to collect metrics for those services,
we provide them with some sensible defaults.

this can not only be handled on ingress level, but we need to mount the
express app also on the app root level. This basically just works out of the
box.