Add Code + Command-Line Function For Upgrade/Migration #11

Version checks need to be in place for 0.1.0, but migration code has been waiting on the first release for there to be versions to check against.

Workflow will be:

• on initial load, confirm version matches, don't proceed if there's a mismatch
• if config newer: prompt user to update PicPocket
• if PicPocket newer, prompt user to update their config
• update process:
  • export/create DB dump
  • run the series of migration scripts
  • rollback on any failures
  • checks to make sure db is in proper order, contents look correct etc