Remove some unused properties.

Refs #10169
Add static function to retrieve resolution parameters

Follows on from how ConvertToYSpace fills the detector parameters
Refs #10169
Refactoring to improve readability

Refs #10169
Add properties to control the number of scatterings, runs & events

Refs #10169
Separate helpers into different file

The main algorithm code is easier to read this way.
Refs #10169