One fixe to MadGraphControl - custom process directory name

Hello,

This is about the possibility to give a name to the process directory - with e.g. output ttbarNLO -f in the proc_card. Currently it doesn't seem to work (anymore) because after the directory is created, the code will try to find a directory with a name such as PROC, and if it can't, it crashes. I think my modification is self-explanatory.

There was one other thing: if the user doesn't give the runArgs as argument to the arrange_putput function, the inputGeneratorFile won't be updated, which can be problematic. I didn't manage to fix this, but I'll mention this here just in case.

Thanks

Tagging MG experts @zmarshal @mcfayden @svonbudd @hmildner and @ewelina