This reverts commit a1eacb900e.
Adding dev outputs to python packages means they can't be included in
a Python environment created with python3.withPackages, because
makePythonPath will include the dev output, which is empty apart from
nix-support, rather than the out output, which contains all the Python
code.
The `buildPython*` function computes name from `pname` and `version`.
This change removes `name` attribute from all expressions in
`pkgs/development/python-modules`.
While at it, some other minor changes were made as well, such as
replacing `fetchurl` calls with `fetchPypi`.
