Spread ditto services equally among cluster nodes

[vladica]

This PR delivers two improvements:

1. Add Pod Topology Spread Constraints to spread ditto services equally among cluster nodes. Each deployment has the ability to set constraints independently.
2. Extract nginx-ingress configuration hard-coded values to the values.yaml file:
   • replicaCount
   • updateStrategy
   • minReadySeconds
   • revisionHistoryLimit
   • resources

[thjaeckle]

Thx a lot @vladica for this contribution.

I also had this on my "todo / to look into" list - this is super useful for maintaining high availability in case of a zone crashing when e.g. 3 zones are available. 👍
So: Much appreciated.