make onUpgrade() more modular so we don't have to re-download all data on every upgrade

[jakewilson]

We should have things to do for specific upgrades so we don't have to drop every table (which is what we do now) and re-download it. For example, adding a new column to the centers table shouldn't cause us to drop the Talk table and take 10 minutes re-downloading it.

[jakewilson]

@bb4242 do you know how many people have downloaded the app? I wonder if, before we officially release the app, we could do a clean restart and set the DB_VERSION to 1? Then we could get rid of all logic in onUpgrade() and from then on we could make it more modular from the ground up, whenever we need to update it. I don't know if this is a terrible idea though. What do you think?

[bb4242]

Yeah, I think that's a great idea. Haha, the total number of installs right now is 2 (one of them is me, and I guess probably @ewoudenberg also; the app is not yet available to the public), so I'd say resetting before releasing to the public would be a great time to do it.