Make installable package

[Evan]

Make lp:daisy and lp:errors installable packages so that we don't need a special python-path argument to the Apache mod_wsgi configuration. We should do this in such a way that it does not break quick iteration in development. We shouldn't have to run dpkg every time we make a change in our personal branches.

[Evan (ev)]

This should also include the current revision number this package was built from, so that we can include it in the http://errors.ubuntu.com footer. lp:daisy should also expose a version parameter so that it can be included as well, as more and more is moving into that module (configuration, launchpad communication).

[Evan (ev)]

It's not possible to run manage.py without this in place as production uses a symlink to the errors directory, which python then tries to interpret as errors-rev-186.