CompressEvents: New algorithm to reduce event workspace memory use

[mantid-builder]

Original Reporter: @jzikovsky

Original Owner: @jzikovsky

Look through each event list, and lump together similar events (events with the same or possible nearly the same TOF/X value); ignore pulse-time (assume that event filtering by time has been completed).

Create a new Weighted event list and if 2 events matched, make one event with Weight = 2 and error = sqrt(2).

Possibly use "rebin"-style parameters to determine how close you consider events to be. It would be wise to use very small bins here otherwise you'd introduce inaccuracies.

[mantid-builder]

This issue was originally trac ticket 2244