Need to allow scaling of qx and qy independently on 2D plot

[butler]

Currently on 1D plots one can change the aspect ratio of the plot by changing the y scale independently of x. This still needs a "manual" interactor (see ticket 16) to set the range by typing in numbers, but teh 2D plot does not allow changing of the aspect ratio. While this is generally a good feature, in some circumstances, such as grazing incidence transforms, where the range of say qx is orders of magnitude different that qy it would be nice to be able to force a non 1-1 aspect ratio to better visualize the smaller q range.

There is probably not a huge call for this at present but as scattering geometries get more and more "sophisticated" such flexibility will likely become more important.

Suggested by Adrian Rennie.

[butler]

had a second request for this in April/May? 2014 from a magnetic scattering person in Europe.