MERGE_RUNS algorithm

[NickDraper]

This is straightforward for runs collected with the same setting, but becomes more complex when dealing with data collected over different frames (e.g., OSIRIS). The simplest solution is to rebin all the runs on a common wavelength scale, add them together and normalise them by the new “reconstructed� monitor. I think this could work, but it requires knowing very accurately where the monitor is relative to the detectors, and I could never do it using the engineering parameters. It would require a procedure to calibrate the monitor position exactly. It is a specific problem with OSIRIS, but we may need it on WISH on Day 1 if we have only detectors in backscattering. I suggest we implement the straightforward part (merging 2 runs with the same chopper setting) and have a separate project on the more complex version.

[NickDraper]

This issue was originally trac ticket 225