Add a linear optimization option to Optimize Recoils or Fluence

[tpitkanen]

(Requested by @mlaitin)

The current NSGA-II multi-objective optimization algorithm is too fancy (slow and inaccurate) for optimizing recoils or fluence. A single-objective linear fit algorithm would run faster and probably yield similar results.

Objectives to optimize (simulated vs. measured values):

• area
• sum

Different local minimums could be presented for the user to select.

The options for algorithms could be displayed like this:

• NSGA-II (slow)
• Linear (fast)

[tpitkanen]

First version is implemented, but this is not complete yet. See #261 for remaining tasks.

[tpitkanen]

This is more complete now, but there are still some major things missing (#262).