MINOR: acme: add the global option 'acme.scheduler'

MINOR: acme: add the global option 'acme.scheduler'

The automatic scheduler is useful but sometimes you don't want to use,
or schedule manually.

This patch adds an 'acme.scheduler' option in the global section, which
can be set to either 'auto' or 'off'. (auto is the default value)

This also change the ouput of the 'acme status' command so it does not
shows scheduled values. The state will be 'Stopped' instead of
'Scheduled'.