Add support for systemd

The service is currently meant to be installed manually by the used packaging system.

Signed-off-by: Simon Busch <morphis@gravedo.de>
Implement static handling of the XDG_RUNTIME_DIR directory

In normal desktop situations XDG_RUNTIME_DIR would be provided when launching a user
session by the environment but as we're not in such a case (yet?) we have to take care
about this on our own. Sadly the site effect is that we have to tell every single launched
application about the correct path.

Signed-off-by: Simon Busch <morphis@gravedo.de>
Merge pull request #17 from webOS-ports/morphis/systemd-support

Morphis/systemd support