Merge fix-1680560-fix-db-package [f=1680560,1680601] [r=blackboxsw] [a=ericsnowcurrently]

Fix the debian packaging.

(fixes lp:1680560)

There were several problems, including unhelpful symlinks, landscape-common installed under Python 3, and conflicts
over the same file.

For now I've marked the two landscape-common packages as CONFLICTS, but
really they should become python2-landscape and python3-landscape, and
the actual common stuff should go into landscape-common. However, that
can wait.