[fcoe] Add plugin to get information about FCoE.

This plugin gets the configuration files present in the
directory  /etc/fcoe and the output of two commands:

- 'fcoeadmin -i' shows information about all FCoE instances, and
- 'fcoeadmin -s' shows information about all discovered
   Fibre Channel Forwarders (FCFs).

Signed-off-by: Jose Castillo <jcastillo@redhat.com>