Add script for renaming of course folders.

As suggested in Gp2mv3#835

Currently, this script supports the following:
- Change of quadri
- Change of course code (either the option like SINF or the number like
  1252)
- Change of course name (like coo, os...)
- Change of course title

In order to make it work and keep the other scripts functional, I had to
change a bit the config.yml, so that it stays with the "names" at the
end of file even after PyYAML's reordering.

Current limitations:
- Has some difficulties when different courses share the same course
  name, as it considers that only one course has a given course name
  (in database parlance, the course name is a primary key). This breaks
  for crypto q7/q8, and also for meca, elec, math etc courses.
- For now, exams and tests have their \hypertitle also updated.
  Maybe we should keep the old quadri/title/course code in old exams.
  Open to discussion (it's a 3 lines fix in the code).
- It leaves the working tree without any addition to Git; maybe we can
  integrate Git with it, so that it git adds the files.
- On Windows, one has to call it using explicitly python; it's more a
  feature than a bug however...
Bad things:
- It's extremely over-engineered probably, but at least it supports
  nearly all corner cases that I can think of.
- Python 3 + Windows + Unicode + PyYAML = nuclear explosion of bugs and
  strange issues.