Change coordinates of bragg peak plotting

[MialLewis]

At the moment Bragg peaks are plotted on the native data coordinate system. This seems to be very inconsistent, especially with regards to logarithmic axis and intensity corrections.

If possible, we would be better off having Bragg peaks plotted using either the normalised data coordinate system (this may not work as required with log axis) or figure coordinate system (this may not work with current zoom functionality).