improv(Compatibility checks): Simple check whether the specified Minecraft...

improv(Compatibility checks): Simple check whether the specified Minecraft version and Fabric/Quilt versions are compatible with each other and available. Enhance VersionMeta for Fabric, allowing for more checks in back- and frontend. The GUI will now only allow valid Minecraft and Fabric/Quilt combinations and present you with an error if you manage to pass an invalid combination.