Add Facter fact that provides information about file descriptors on the system.
Add Facter fact that provides information about file descriptors on the system.

This fact provides information about file descriptors currently available on
the system as follows: total allocated file descriptors since system power-up,
total free file descriptors available for allocation and maximum available
file descriptors (also known as "RLIMIT_NOFILE" which per-process and always
lower than the constant "NR_OPEN" denoting Kernel enforced upper-limit) and
which is probably the most useful piece of information in its own right ...

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

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