Rename config option AuthPath -> AuthDir.

Dir suffix is more logical and more consistent with other options like
ThemesDir, FacesDir etc.
Set MaximumUid default value to 65000.
make the systemd file reflect the install dir
Update CONTRIBUTORS.
Check for systemd instead of libsystemd-daemon. Fixes #31.
Clock: Allow setting time and date fonts seperately.

Now we dont use custom font for date in maldives and maui themes, this
should fix issues with native characters. #30, #32