Added documentation for the rrdd.py library.
Added documentation for the rrdd.py library.

Signed-off-by: Rok Strniša <ef2e6fb7f9c4d68ca2b20c62606309353789e818@citrix.com>

koushikcgit/xcp-rrdd,koushikcgit/xcp-networkd,djs55/squeezed,koushikcgit/xcp-networkd,simonjbeaumont/xcp-rrdd,sharady/xcp-networkd,djs55/xcp-networkd,simonjbeaumont/xcp-rrdd,djs55/xcp-rrdd,djs55/xcp-networkd,koushikcgit/xcp-rrdd,sharady/xcp-networkd,johnelse/xcp-rrdd,robhoes/squeezed,koushikcgit/xcp-rrdd,djs55/xcp-rrdd,johnelse/xcp-rrdd