Remove obsolete upgrade code

Master, and the next release Real Soon, is data-incompatible with previous releases. That means upgrade code can go away.

Three pieces:
- Assigning UUIDs to tables, columns on start-up. They are now always assigned at creation.
- Accumulator ordinal migration. Ordinals now exist in the Protobuf.
- Protobuf treeName migration. They now exist in the StorageDescription.

Only the last one had the potential to cause an incompatibility with data sets from recent builds, but I left the gap in the Protobuf as to not. We can get rid of the gap if/when we significantly change that.