Add MySQL (MariaDB) support

[Preloading]

This PR should add MySQL (mariadb) support to 3DS-RPC. Using MySQL has various benefits over SQLite like easy backups of the database, and allows the processes to write to the database at the same time.

It's not exactly the neatest, but it works.

Made discord.py work, but discord rpc isn't really tested.

To enable MySQL support, change IS_SQLITE to false, then fill in all the auth stuff.

pls push pretendo to 3dsrpc.com

kthxbye