Extend functionality of Explore tab to reflect peak width variability at different 2θ

[koshchii]

Change of the peak width (in γ°) in Statistics section of Explore tab has to be simulated upon the motion of the 2θ-slider. Random numbers can be used for the front-end implementation.

Additional new tab that displays Peak width as a function of 2θ should be considered. If the calculation is fast, this tab should be simply provided to the users. Otherwise an additional button to trigger the calculation might be needed.