This commit renames the pythondaemon module to match its module name, github
name, and pypi name, which makes it easier to find and reference. In order to
avoid breaking any external users, I've left an alias with a deprecated warning.
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`.
