Adding filename checks for illegal characters

[OnSive]

Please test this solution, don't have the needed refs to build the mod.

To test: name your server with any illegal character on your platform (with exception of zero space chars, hope that nobody uses them). The code should remove them or completely replace forbidden file names with FORBIDDEN (yea, I know, I'm really creative)

[ghost]

It's still missing the other half of the code that allows the loading of a save for a server that had illegal characters, but it's a pretty good starting ground if anyone wants to pick this up

[ghost]

Closing this since it's no longer compatible / needed with newest version. Still thank you for the colaboration