Add Facter fact that provides information about default gateway.
Add Facter fact that provides information about default gateway.

This simple fact exposes information about the default gateway (or
the "route of last resort" if you wish) that is available on the
system.

Signed-off-by: Krzysztof Wilczynski <9bf091559fc98493329f7d619638c79e91ccf029@linux.com>

kwilczynski/facter-facts,benedikt-wegmann/facter-facts