setuptools and zc.buildout.

Don't upgrade if the buildout command is non-local.

  setuptools as one of its dependencies, we now treat setuptools as an 
  implicit dependency.  We generate a warning if the distribution
  is a develop egg.

- Remove old develop egg links. This requires storing the old link
  paths in .installed.cfg.

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Non-zip-safe eggs were not unzipped when they were installed.

__file__ to fail.

paths were used, causing setup to fail when run from a different
directory.

Updated release information.

versions.

Fixed a bug in installing by direct egg download.

the version of python used to run the tests is not Python-2.3.

Use pypi as the index when running these tests. This is,
unfortunately, necessary because when installing a source distro for
another version of Python, we need to download setuptools for the
desired version.  Maybe in the future we can figure out a way for the
tests to use a local copy of setuptools.

egg is not important.

API. This allowed the tests to be simplified somewhat.

https://launchpad.net/products/zc.buildout/+bug/60582

Don't use extensions when bootstrapping.

This makes things go a little faster, makes errors a little easier to
handle, and allows extensions (like the sftp extension) to influence
more of the process.

adding sftp support to buildouts that need it.