Improve grader help message about selfie HOT 1 CLOSED

➜  selfie git:(grader-argparse) ✗ ./grader/self.py -h
usage: ./grader/self.py [-h] [-q] [-b <file>] [-d <directory>] [assignment]

The Selfie autograder

The autograder is a tool that gives students and teachers the means
for evaluating assignments that shall extend or adapt Selfie with
concepts learned in the lecture.
It also enables teachers to fetch and grade multiple Git repositories
in one go.

It is part of the Selfie project of the Computational Systems Group
at the Department of Computer Sciences of the University of Salzburg
in Austria (http://selfie.cs.uni-salzburg.at).

For more detailed information about its usage, please consult the
enclosed README.

positional arguments:
  assignment      The assignment to test

optional arguments:
  -h, --help      show this help message and exit
  -q              only the grade is printed
  -b <file>       bulk grade assignments defined by a file with github commit links
  -d <directory>  path where all bulk graded repositories should be saved

General Assignments:
  self-compile
  print-your-name

Compiler Assignments:
  for-loop
  bitwise-and-or-not
  array
  struct-declaration
  bitwise-shift-compilation
  array-multidimensional
  hex-literal
  bitwise-shift-execution
  struct-execution

OS Assignments:
  threads
  lock
  processes
  fork-wait
  assembler-parser
  self-assembler
  fork-wait-exit
  treiber-stack