Refactor version migrations to attempt only one time

[mbryzek]

This change is intended to:

• avoid needless attempts to upgrade application versions to latest spec. We do this by tracking migrations explicitly in a table named migrations and attempting one time only, recording any errors
• Fixes a bug that required us to have the service json to migration (not needed if we have the original)

We upgraded lib-postgresql-play in this change as well to support the in2 feature. This also required refactoring Symbol which has been deprecated.

• DB