enabled active record caching

r6189 enabled active record caching. At least that's what it says it
did and it does seem to have.

This appears to have the impact of always requiring a database. Before
this change, I was able to run my non-db rails apps without a
configured database with was very convenient for some of what I do.

Could we make this configurable? (Or is it, and I just don't know how?)

Sure: the query cache will only kick in if you’ve configured Active Record.