Add pydoc documentation to akanda driver modules

This patch provides pydoc documentation for the following akanda driver
modules:

arp
base
bird
dnsmasq
metadata
ping

Basic documentation has been provided for all methods, but some are
missing specific type, param, and rtype docstrings.
pep8 compliance

Some whitespace was leftover from pydoc formatting.  This patch cleans
up this whitespace.
More pep8 compliance

Fix some lines with 80+ chars.
Fix grammatical error in pydoc comment
Populate rtype docstrings and update some params

Updated the rtype docstring for a few methods in a couple of modules and
provided a param description for interface_mapping.
Merge pull request #86 from drwahl/linux

Add pydoc documentation to akanda driver modules