Update Agent features

[maffettone]

If you make a Pandrosus object at the ipython command line, the tab key works even on the attributes of the group attribute. So you can use introspection to figure out what the arrays are called. In short, the energy axis is .energy, the wavenumber axis is .k and the Fourier transform axis is .r. .mu, .norm , .chi, and .chir_mag are the most commonly plotted data arrays, although there several other interesting one. https://xraypy.github.io/xraylarch/xafs.html

[maffettone]

Going to fix this to two possibilities for now.
chi(k)
mu(energy)