Update CsServer.cs to accept workshop maps from "workshop_maps.json"

[gubsy420]

Updated SwitchMap() in CsServer.cs to accept a list of workshop map names and their corresponding workshop IDs from a new configuration file located in csgo/PugSharp/Config called "workshop_maps.json". An example of the expected workshop_maps.json format can be found below:

{
  "de_cache": "3437809122",
  "de_cbble": "3437319455",
  "de_vertigo_45": "3276886893"
}

workshop_maps.json

[Apfelwurm]

Just for reference, this would partially solve #153 , but i think this is a solid way to make the feature work for now. Thanks @gubsy420 for your work!
I think in the long run we should think about a way to additionally implement the idea from the issue, so this can be fully configured using a loaded configuration. But i think for compatibility reasons we would need this approach anyways, so imho every thing else could be implemented later :)