Remove support for Ehcache

[Luke-Sikina]

Currently we have three caching solutions:

• No cache
• Redis cache
• Ehcache

To the best of my knowledge, no one uses ehcache aside from the MSK private portal. Generally, a feature that is not used is a feature that accumulates bugs. I propose that when we switch the MSK portal to Redis, we remove the Ehcache option. This has a few advantages:

• Wiring: if we remove Ehcache, we can just always wire the redis cache, and disable it at runtime. This allows us to only create one docker container that serves all our caching options
• Simplicity: no confusion over what cache to use

[jjgao]

@cBioPortal/backend