SB database cleanup

* PEP8 fixes for db.py
* Cleaned up the db version check wording, raise SystemExit exception with message to match how we handle other startup issues.
* Added db version min check since we no longer are going to support migrating 2+ year old dbs.
* Updated initial db schema to latest (based off build 501).
* Trimmed down the SB db migration process to only support build 496+ (2012-06-28)

  > which covers the major migrations but allows us to eliminate a lot of legacy things that were not done correctly.