Overlaps when using geant4 integrator set for rbend with poleface rotation

[Laurie Nevay]

In the case with

option, integratorSet="geant4";

we actually build the pole face angles correctly. However, the drifts do not match now for an rbend with a pole face rotation in this case. I suspect a bug in some logic near the top of component factory with drifts.

Example input file attached.

‌

[William Shields]

This was caused by the look ahead logic finding the zero length unangled multipole instead of the dipole. BDSIM now skips over all thin elements and get the face angles from the next/previous 'thick' elements. Fix has been pushed to the develop branch.