Create gitconfig, and symlink KDE env

- Add a step in the "setup-unix" target of the Makefile to create a symlink from
  the environment file to ~/.kde/env/environment.sh, since KDE requires the file
  ended in ".sh".
- Finally fix the issue of not having the git configuration under version
  control. The ignore-patterns file is now symlinked to the root of the home
  directory, so the gitconfig file is always the same in all my machines.