Imported Thomas Nagy cs.py module

I will start mergin the cs_extra.py into cs.py.
Using resx.py from waf extra tools

This is a better implementation then the version in cs_extra
Merge remote-tracking branch 'origin/master'

* origin/master:
  Help script to include monogame libs in your project
  We using pkg allow fallback to using dev libs
  Added a check_nunit function
  Rename cs.py to cs_extra.py
  Us ctx.env in check_extlib and not a copy
  rename waftool to extra
  Added install_native_lib function.
  Added env param in check_extlib
  fixed check_pkg func to omit the keyword argument package
  Copy .config file to build directory