alternative needed to --user installation

[johannct]

currently the prescribed usage of sn_pipe is to build the pipeline via the custom script pip_sn_pack.py, which hardcodes call to pip with the option --user. I think that a production installation will need to avoid installing packages in a user dependent local area.

[johannct]

Here is a setup that I used to build a local install out of .local, but it does not run anymore with the pip_sn_pack.py machinery
setup.py.txt