Only load crm-initial.conf when the file got changed

There is no point in loading it if it's the same as before, since we
already imported these settings.
Make stonith-enabled/no-quorum-policy variables in crm-initial.conf

The values will change depending on options in the wrapper, or other
factors.
Add a STONITH recipe

By default, STONITH is marked as disabled. It can be enabled and
configured:

 - manually (by the user)
 - with a stonith plugin that will be used with a clone resource
 - with a stonith plugin that will have per-node parameters
Add support for IPMI as STONITH in crowbar-pacemaker

Since Crowbar can know about IPMI configuration of nodes, we can
translate this into a valid STONITH configuration.
Add attributes for STONITH
Add validation for stonith bits of the proposal
Compute no-quorum-policy based on number of members in the cluster

This is "ignore" if we have 1 or 2 members, and "stop" (the default) for
more members.

We do this magic in the crowbar-pacemaker cookbook, since we have the
required information there.
Check that the specified STONITH plugin is available

We simply need to check if the plugin is in the output of "stonith -L".