calculate_orbital_wavelength_variation is very broken

[nabobalis]

calculate_orbital_wavelength_variation has the following problems (among others):

• bad_aux is not used
• slit_axis is not defined
• gaussian1d_on_linear_bg is incorrectly called
• raster is not defined.
• date_created is not defined
• abswvl_nuv is not used

Further:

• It is too large, it needs to be split into smaller pieces.
• No tests.
• Needs to be checked with the IDL version.