debian: pythonify debian pkg artifacts

This adds the basic boiler plate to control and rules for contructing a
python package.
debian/control: corrected 'Priority'

Changed 'extra' to 'optional'.

'optional' packages include various applications that a user may want to
use, whereas 'extra' packages are defined as those which "conflict with
others with higher priorities". See
https://www.debian.org/doc/manuals/debian-faq/ch-pkg_basics#s-priority.
debian/control: updated maintainer
debian/control: restored strict python version req

For now, require python < 2.8 (which means not python 3.x).
Merge pull request #20 from larsbutler/pythonify-deb-pkg

Pythonify debian package
zvsh: escape nvram values more consistently

I dug into the ZRT config parser code and believe this should be a
more correct and complete way to escape the values we put into the
nvram files.

Before, a command line argument like '"quoted"' would have been put
into the nvram file as

  args = "quoted"

and this is wrong: the outer quotes are removed by ZRT when is parses
the nvram file. We now correctly escape double-quotes as well as
space, comma, backslash, and newline.
zvsh: expand command about escaping cmdline args
zvsh: fix long line