Mjansen/buildsytem relative

I am working on better install into a prefix != /usr . For now only on the python library and scripts paths to enable support for install into python virtualenv or pyvenv installation. For that relative install path are required.

To see the differences introduced issue before applying the patches
$ python setup.py install --prefix=/opt --root=$PWD/before_opt
$ python setup.py install --root=$PWD/before
and after applying them:
$ python setup.py install --prefix=/opt --root=$PWD/after_opt
$ python setup.py install --root=$PWD/after

before/ and after/ should be equal before and after the patches are applied (apart from some timestamp related issues).

before_opt and after_opt differ. In after_opt nothing is installed into /usr/. Into before_opt there is.