Pupil Detector install.py, do not assume fixed folders

[behinger]

When trying to compile setup.py in pupil detectors it assumes that opencv, eigen3 etc. are at fixed places.
This is not the case for our setup

I have several ideas how to improve this:

• check if the path exists and throw an error otherwise
• user specified paths
• auto detect the libraries from the LD_LIBRARY_PATH

[papr]

Using pkg-config would be an other option

[papr]

This issue has been resolved by extracting the pupil detectors into a separate repository with a proper setup.py procedure.