Update setuptools (5.0.1 -> 5.1) (refs #196)
Add pseudo `ensurepip`
Enable pseudo _ensurepip_ for existing definitions
Rename functions

  * `build_package_setuptools` -> `build_package_ez_setup`
  * `build_package_pip` -> `build_package_getpip`
Pass ez_setup.py and get-pip.py via argument instead of STDIN

AFAIK, Jython 2.7b2 could not handle ez_setup.py via STDIN
s/getpip/get_pip/g