Use dynamic resource paths relative to the script location

[fridrich]

Hypnotix hardcodes /usr/share/hypnotix and /usr/share/locale for its UI files, CSS, pictures, country list and translations. As a result it only works when installed under /usr.

This change derives the paths from the script's own location:

• PREFIX = two levels above hypnotix.py (<prefix>/lib/hypnotix/hypnotix.py → <prefix>)
• PKG_DATA_DIR = <prefix>/share/hypnotix
• LOCALE_DIR = <prefix>/share/locale

os.path.realpath resolves symlinks, so a symlinked script still finds its data.

For the standard /usr install, the resulting paths are the same as before, so packaging is unaffected. It also makes Hypnotix work:

• when installed under another prefix, e.g. /usr/local or /opt
• when run straight from a git checkout (./usr/lib/hypnotix/hypnotix.py), which is handy for testing changes without installing. The GSettings schema still needs to be installed.

Not changed: /usr/share/circle-flags-svg belongs to an external package, and the usr/bin/hypnotix launcher still calls /usr/lib/hypnotix/hypnotix.py.