Refs #10247. PoldiPeakCollection can now store a point group

If a PoldiPeakCollection is created from a CrystalStructure, it can be useful to at remember at least the point group from which it has been created.
Checkpointing work on PoldiIndexKnownCompounds.

Refs #10247.
Refs #10247. Added unit tests, small refactoring
Refs #10247. More unit tests
Refs #10247. Cleaning up, documentation
Refs #10247. Tolerance is absolute, not relative.
Refs #10247. Started wiki page for PoldiIndexKnownCompounds
Refs #10247. Changed score calculation, tolerance relative again.
Refs #10247. Copying parameters from measured peaks.
Refs #10247. Small changed, some cleaning up.

Removed the multiplicity weight option, as that will be covered elsewhere.
Merge branch 'feature/10247_index_poldi_peaks_with_known_cell' into develop