corrected variable names in calcEigenRaysRF(). closes #28

This function made use of a lot of non-descriptive loop variable names
(like i, j, k, l) with changing meaning throughout the code -what an
ugly thing!

Anyway, changed to things like iRay, iArrayR, iArrayZ, etc and the bug
quickly became apparent (using i instead of k at some point).
minor bug fix
Merge branch 'development' of https://github.com/EyNuel/cTraceo into development