Discouraged file path can be specified on the command line

[tirix]

No description provided.

[digama0]

Since regen_discouraged and output_discouraged are basically the same thing now, I combined them into one function and moved the file handling into the command line tool itself. Also the scope pass is not necessary for discouraged generation, so I made it optional and now it only takes 241ms to generate the discouraged file for set.mm.

[tirix]

Ok for the changes!
I just think the dummy closure is maybe a bit hard to read. I wanted to propose a small change but I was just one minute too slow, so I created a new PR, #98