Use long form command line options

[yeban]

For example --min-length instead of -m.

(@yannickwurm's idea)

I believe this is already the case for practicals 1-3. Short form is used in practicals 1-3 when it is the only option (sorry if I missed any). I don't think this is relevant for practical 5.

Practical 4 can further improve in this regard.