3d Plots can take a long time to process with no progress

[mantid-builder]

This issue was originally TRAC 8285

Original Reporter: Keith Brown

I've found that asking for a 3D plot from a larger Matrix Workspace takes a rather long time, and there is no progress indication as to how long it'll take.

On windows, while it's processing, mantid acts like it's no longer responding.

This should really be improved so that mantid stays responsive to some level while it's processing a large workspace, and giving some feedback from it would be nice. The ability to cancel this process would also be welcome.

[mantid-builder]

@NickDraper (2014-02-14T11:07:58):
bulk move to assigned at the into of the triage step