Add Normalisation option to Rebin2D

[Nick Draper]

We need to be able to control how the data is accumulated in Rebin2D particularly when this is used to create a 1D slice with a thickness.

Right now we normalize by the contributing fractional area, which effectively divides by the number of contributing pixels. But often people want to integrate across the thickness, not average across it. So we need to add an option to control how we normalise the data across the axis.

What I'm not clear about is how best to do this in parameters. Care to make a suggestion?

[Owen Arnold]

There was a sketch on our whiteboard that would make things clearer as to how it should be behaving. That would be useful against this ticket.

[Nick Draper]

Moved to Backlog at the code freeze of release 3.2

[Peter Peterson]

Review and see if this should just be closed.

[Stuart Campbell]

This ticket has been transferred to github issue ​9982