Create: warn when a metadata format's platform components are missing

Create: warn when a metadata format's platform components are missing

If the metadata handler can not find its platform support components
then there is no way for it to verify that the raid configuration will
be supported by the option-rom.  Provide a generic method for metadata
handlers to warn the user that the array they are about to create may
not work as intended with a given platform.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>