Simplify creating Raypath

[joha2]

Typically raypaths are generated in three steps:

• (o, k, E) = collimated[divergent]_bundle(num_rays, start_dict, wave=wavelength)
• initialbundle = RayBundle(x0=o, k0=k, Efield0=E, wave=wavelength)
• raypaths = s.seqtrace(initialbundle, sequence)

Implement these three steps into a convenience function. This is necessary since drawing, optimization and spotdiagramms usually need different number of rays or ray fans.