XRD parser functionalities

[andreaa93]

add the phi scan and the rocking curve parsing

[ka-sarthak]

There was an E-mail correspondence with Oliver Bierwagen (PDI) to figure out what is currently supported and what more needs to be implemented. This is an effort to make the plugin more versatile for more types of XRD scans. Here's some of the key points:

• The result section is populated with phi and omega positions even if they are vectors. But the plotting always expects two-theta to be the x-axis for the intensity plots. For Phi and Omega scans done at fixed two-theta, we want the plots to pick whatever position is being varied as the x-axis.
• In the case of the two-theta-omega-scan (rocking curve), both omega and two-theta positions are vectors. Currently only the intensity vs two-theta plot is generated. We want to incorporate visualizations for the omega position as well.
• We need to add support for texture maps, also known as chi-phi scans done at fixed two-theta and omega, where multiple scans are conducted by varying chi and phi (denoting the sample rotation and tilting). The resulting visualization is a pole figure (polar plot) to look at the dependence on chi for a fixed phi position.

Adding @budschi for visibility
@aalbino2 Can we also add Oliver here?