User can now configure the list of device classes to detect, either via
a configuration file or by using the --options command line flag.
An example of a command line flag to detect all network controllers and
("main class 0x02) and VGA display controllers ("main" class 0x03 and
subclass 0x00) would be:
--options='{"sources": {"pci": {"deviceClassWhitelist": ["02", "0300"] } } }'
Support yaml/json based config file for nfd. This commit does not add
any actual consumers for the config file, yet.
By default, nfd tries to read
/etc/kubernetes/node-feature-discovery/node-feature-discovery.conf.
This can be changed by specifying the --config command line flag.
