* Replace $(PKG_NAME) with package name in call, define, and eval lines
* Remove extra "define" in $(call define Package/.../description)

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

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>

Signed-off-by: Josef Schlehofer <pepe.schlehofer@gmail.com>