Improve activation monitoring option processing

Improve activation monitoring option processing

. Add "monitoring" option to "activation" section of lvm.conf
. Have clvmd consult the lvm.conf "activation/monitoring" too.
. Introduce toollib.c:get_activation_monitoring_mode().
. Error out when both --monitor and --ignoremonitoring are provided.
. Add --monitor and --ignoremonitoring support to lvcreate.  Update
  lvcreate man page accordingly.
. Clarify that '--monitor' controls the start and stop of monitoring in
  the {vg,lv}change man pages.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>