Have a better story around local caching independent of the crawling stages

[ScottMansfield]

The fetch, parse, and (maybe) index pages should heavily use caching to prevent duplication of work. The cache right now is either a frail connection to a single EC2 instance, or an in-memory in-process cache that does not survive restarts. A local option should be easy to do.

Probably a gradle task with dependsOn should do.

[ScottMansfield]

Running a local redis server seems to work, but it's still not ideal since it requires redis to be installed.