Updated Postgres naming of objects

[ryanbooz]

@HuxleyKendell and I were working on the updated script at the same time (great job, Hux). I'm submitting this as an update to consider because of how Postgres names objects. All objects are coalesced to lowercase unless they're quoted, but then all objects need to be quoted from that point forward if they are anything other than lowercase. Therefore, the Postgres convention is to use snake_case, which is used for all other internal functions and naming.

This becomes evident in the baseline script, where all of the creation statements are all lowercase (rather than the CamelCase of the creation script), and then automatically generated objects like sequences are snake_case.

I also made updates to the identity columns so that they would function like SQL Server identity columns (cannot insert values manually), and created some procedures rather than functions. Essentially, any function that does not return a result (void) can technically be a procedure. These changes are debatable, but I thought having the opportunity to show that both are maintained by Flyway was potentially helpful.