resolution documentation is in two places

[pkienzle]

In the documentation for the resolution calculator (sasgui/perspectives/calculator/media) there are some diagrams that would be useful to include in the sasmodels description of resolution.

Check that these two docs are consistent, and maybe put the theory description entirely in sasmodels and reference it from the resolution calculator docs.

Similarly, gen_mag_pic.png in this directory is very similar to the M_angles_pic.png file in sasmodels. Maybe reference the magnetic scattering theory in sasmodels from sas_calculator_help? The general scattering theory would also be useful to have in sasmodels.