Add validation for proposal

We validate the database engine as well as the HA bits.
Add DRBD support for HA

Co-Authored-By: Vincent Untz <vuntz@suse.com>
Split the colocation / order constraints

Since we first create the filesystem-related pacemaker resources and
then do some actions on the filesystem before creating the other
pacemaker resources, we need to have the constraints in place forthe
filesystem before we do the actions on the filesystem.
WORKAROUND: cleanup the resources
Always use a pacemaker group

The colocation / order constraints are actually only really needed
between the master-slave and the filesystem, and since we split that
part out, we can then simply use a group for the rest.