Track database update schedule in rnc_database

[blakesweeney]

We should add a column to rnc_database that tracks the udpate schedule for databases. Currently, that is just something we know but never record anywhere. Instead we should add a column that tracks it. We can then use this as part of our weekly updates by having the pipeline only update those marked as weekly. That might take some tweaking of the pipeline config, but I think it would improve things. The current set of update schedules are:

• weekly (runs every week)
• release (runs every time we do a release)
• once (only runs once, release or otherwise)