Remove user directory path assumptions

Created by: mitchty

Where I work /home is an automounted nfs directory. Local users are installed in a different local directory.

So instead of assuming that /home/git is the git users home directory, use the Etc module to get the configured home directory for the Settings.gitlab['user'] value (normally git).

The new setting is named user_home, unoriginal but works well enough could be changed to whatever. Users with /home/git as their home directory will not notice a difference.