Remove width restriction on size_in_bytes

The UR update classes from db command (PR #52) appears to have added a standard integer width restriction to this column even though the underlying column type is bigint.

This removes that.
Oh, is that a goal going forward? It seems like that substantially limits our ability to do metaprogramming (we had to revert another part of it in PR #82 and I think there are other places where it didn't explicitly break, but it didn't "do the right thing" due to metaprogramming.

Either way, I agree we should add bigint to UR::Value for sure.