This updates all Python packages that download their source from PyPi to
use pypi.mk.

This will allow future improvements/changes to pypi.mk to affect all
relevant packages.

This also makes it easier for future Python packages to start using
pypi.mk, when it's clear how it is used in existing packages.

Signed-off-by: Jeffery To <jeffery.to@gmail.com>

If a package builds python & python3 variants, then the respective
PACKAGE-python* conditional DEPENDS were added, since circular
dependencies should all be resolved now.

Signed-off-by: Eneas U de Queiroz <cote2004-github@yahoo.com>

Signed-off-by: Daniel Danzberger <daniel@dd-wrt.com>