[Feature] Config "sets", and selecting a config per-match

[BloodyIron]

In most cases the config we will want to use won't change. But there may be some cases (Arms Race/Demolition) where we want to select a specific config, without having to kick to CLI to switch the default config.

If we could upload config files through the webGUI, and make them "selectable" at match creation (and if we could mark a config as "default" in the config section), this could help quite nicely. ESPECIALLY if we need to make config changes!

And then if we could have the match list the name of the config being used, on the match page, I think that would be handy too.