Merge remote-tracking branch 'origin/feature/7216_normalisetomonitor_crash'
Retrieve an ion by string containing both symbol & charge.

Refs #7020
Add form factor attribute to quantification models.

Allows the user to specify the form factor type or turn it off without
coding a whole new model. Refs #7020
Fix formFactor constant when turned off. Refs #7020
Merge remote-tracking branch 'origin/feature/7020_quantification_formfactor_switch'
Re #7026. Split DiffSphere into three files so wikitools can find it.
Merge branch 'feature/7026_rename_fitfuncs' into develop