Not all layouts have a variant named "basic". So we should
allow empty variants and also make it default.

probing will be done by kernel,
* bin/mudur.py (checkFileSystems): Delete /forcefsck only if it
exists. Fixes an unhandled exception during boot if mudur=forcefsck
is given,
* bin/mudur.py (readyService): Remove this method and use startService
with a second parameter equal to 'ready' instead of this,
* bin/mudur.py (startService): Add a second parameter command= for
being able to call "service --ready" for some services.
* bin/mudur.py (Config.__init__): Enable debug by default as we don't
flood mudur.log with millions of lines when it's enabled.

	* bin/mudur.py: The I/O redirection of start-stop-daemon
	doesn't work at all. Implemented a new method run_async()
	which runs a command in background and optionally redirects
	its output and error streams.
	* bin/mudur.py (startUdev): Use run_async() for spawning
	udevadm monitor instead of buggy start-stop-daemon.