Add MariaDB support (#156)

* Fixed startup db check

* Relation tables are created automatically for IGDB metadata

* Removed JSON dependency from filters

* Removed JSON searches from Game library queries

* Gaseous now runs without error on MariaDB

* Fixed static database name bug

* Updated docker files and README

gaseous-server/Classes/Metadata/GameModes.cs

@@ -2,7 +2,6 @@
 using gaseous_tools;
 using IGDB;
 using IGDB.Models;
-using MySqlX.XDevAPI.Common;
 using static gaseous_tools.Config.ConfigFile;
 
 namespace gaseous_server.Classes.Metadata