Added SQLServer Support

[BoySanic]

Hey again!

So I've made some changes to allow for Microsoft SQL Server to be used as the SQL Server backend.

I thought initially it'd just be a driver, but a lot of the queries used in EternalJukebox needed some adjustments to be compatible with T-SQL's syntax.

The MERGE statements you're seeing is how upserts are implemented in T-SQL, and checking that a table exists is a little more involved in T-SQL (should be able to see what I was doing with it).

I've tested this. It builds, and DB functions work on Microsoft SQL Server with these changes in play.
(Mainly I was checking that my check for mysql or sqlserver was working, which it does)

I haven't tested mysql, but I could spin up a box and try it out if you wish.

Please let me know if you have any questions!

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This change is