Introduce log levels

Signed-off-by: Michael Buesch <m@bues.ch>
coreserver: Forward maintenance requests

Signed-off-by: Michael Buesch <m@bues.ch>
coreserver: Transfer loglevel via environment

Signed-off-by: Michael Buesch <m@bues.ch>
coreserver: Tighten the outer cycle loop

Signed-off-by: Michael Buesch <m@bues.ch>