Fixed mods not loading from `app_extra_mod_path`

[ohlidalp]

Fixes #3149

Problem was caused by myself in 74ed1083cb9e53e38096ec96b6a7b1f0b237ce01 - apart from fixing the bug, I also made a cosmetic edit of resource group names - Instead of it being 'bundle $FULLPATH', I made it '{bundle $LOCALPATH}'. But I botched the code, causing exception "invalid string position" to be thrown.

Solution: keep pretifying the resource group names, but account for all locations. I added a location-label to the name to avoid RG name clashes.

• prepackaged mods, i.e. {bundle BIN:\content\simple2-terrain.zip}
• extra mod path, i.e. {bundle EXTRA:\DI_SportsCar.zip}
• mod dirs under user profile, i.e. {bundle USER:\mods\vehicles\Desperado.zip}

[RoRAustin]

Able to successfully load into a terrain and vehicles from extramodpath now. 👍