Prep for refactor for geometry class

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Refactored geometry such that angles are always phi_fi0, phi_fis, etc. rather than phi_i0, phi_is to allow for more flexible geometry

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
More refactoring to deal with symmetry/asymmetry

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>