Linux anathema.sh overhaul

Do not force users to install anathema on /usr/share/anathema
This patch will use standard shell scripting to detect the real
anathema installation folder.

When invoking anathema.sh if an argument is provided this will
override the default repository path.

I made this patches on Anathema_2e because it's the one that I use, I've checked the master branch and this 2 commits can safely be cherry-picked