Fix for too-generic egg-links

The too-generic `develop-eggs/*.egg-link` files that used to point at `/usr/lib/python/dist-packages` and so are now replaced by symlinks to their actual directories and a copy of their egg-info files. The latter are needed for the symlink to the directory to work.

See changelog entry.

It seems like it works wonderfully in a local test... You might have to do a one-time-only zap-all-dev-eggs action to get rid of the current ones. But that's a BBB problem. Perhaps that one is solveable with another `develop-eggs/EGGNAME.egg-link` os.remove action?