Use socket module to provide an IPC mechanism.

Use socket module to provide an IPC mechanism.

Guardian now supports inter-process-communication based on
an UNIX socket, which is based on the guardians socket module.

All recieved messages via socket automatically will be accepted
and parsed. If they are valid, the corresponding events will be
enqueued into the main event queue of guardian.

Signed-off-by: Stefan Schantl <stefan.schantl@ipfire.org>