Add built-in cache-aside caching w/memcached

[bmonkman]

Should include:

• Support in backend for memcached (Go and/or Node)
• Support either custom or via library for cache-aside caching w/invalidation
• Read from cache. On miss, read from db and write to cache.
• On update, delete from cache.

[sshi100]

Kubernetes kustomize/base variables ready for cache, created by infrastructure.