Preparing for the SOXS 0.5.0 release

[jzuhone]

This PR will serve as the launching pad for the SOXS 0.5.0 release. A summary of changes:

• The PSF can now be set to None (or null in JSON files) in an instrument specification for no PSF scattering of events.
• The particle background can be set to None (or null in JSON files) in an instrument specification for no particle background.
• A faster progress bar, tqdm, is now in use in SOXS.
• Fixed a minor bug in the interpolation of APEC tables for thermal spectra. The difference in the generated spectra is small, at around the fifth decimal place.
• Added a constant spectrum generator, soxs.spectra.Spectrum.from_constant.
• Added ellipticity and angle parameters to soxs.spatial.RadialFunctionModel objects to create models with ellipticity.
• Added flat-field coordinates to soxs.spatial.SpatialModel objects.
• Made public subclass of soxs.spectra.Spectrum objects, soxs.spectra.ConvolvedSpectrum, which is a soxs.spectra.Spectrum convolved with an ARF.
• Small internal changes designed to provide a more seamless interface to pyXSIM.

• Three new tools have been included to produce derivative products from event files:

  • soxs.events.write_image: Bins events into an image and writes it to a FITS file.
  • soxs.events.write_spectrum: Bins events into a spectrum and writes it to a FITS file.
  • soxs.events.write_radial_profiles: Bins events into a radial profile and writes it to a FITS file.

[coveralls]

Coverage increased (+0.7%) to 80.717% when pulling 5968e46b25a06aadf525a290c8c0b543ef9c450e on jzuhone:pyxsim into 825b720a5eb51cf9b138befeafab87b080b6fcca on XRStools:master.