Feature: various: merge clone resource type and master/slave resource type

Rather than a separate resource type, master/slave clones are now represented
as clone resources with the "promotable" meta-attribute set to "true".
The old syntax remains supported for backward compatibility, but is deprecated.

This breaks API backward compatibility:

• enum pe_obj_types: the pe_master value has been removed, and the pe_container value has changed value

• libpe_status: get_resource_type() and get_resource_typename() are no longer available as part of the public API