teacup cache

This is a teacup subcommand that is used to manage the teacup cache settings.

[TODO: Describe what it does]

DKF: If you're having problems with the cache not being used, you may need to increase the teacup timeout. I had to do this because the default setting (30 seconds in the version that came with 8.5.0) was not enough to download the metadata DB (~12MB compressed) over my 2Mb link.

Also note that the DB is updated once per day.