indexing - remove/avoid/tag duplicates

[jonwright]

If two grains are the same within hkl_tol then we should look into merging them...

[jonwright]

Note from #81": To deal better with overlaps, and try to overcome a few recurring problems:

• Can we convert columnfile.py into a pandas dataframe ?
• Raw peak data in one table (x,y,omega,intensity etc)
• Detector geometry applied -> XL, YL, ZL : adds a new table depending on geometry
• Depending on (UB)+Diffractometer -> OmegaCalc : adds a new table for each grain
• Depending on (translation+omega) or (translation+OmegaCalc) -> tth/eta/k/gv/hr/drlv
• A peak to grain assignment matrix should be very sparse. Currently only one grain per peak. It would help for twins and duplicates to store the N grains per peak which might be able to index.

The rest of the this would imply a bit of reorganisation to update the geometry to pull out detector versus diffractometer + grain computations.

[jonwright]

Transfer this to #5