main: Add new option to all daemons

This commit adds a possibility po pass additional options to all daemons
on the command line using syntax like:

  mfsmaster -o something_special -o another_tweak=yes start
  mfsmaster -o some_feature=3 stop

It would make it possible to implement a couple of new features.
Documentation (manpages) will be added in the future.

Change-Id: I2c477e0e3e346a5f04f90afa986e5822585fdbb4