Refs #10282. Add IScatterer
Refs #10282. Checkpointing work.
Refs #10282. Expanding interface of IScatterer
Refs #10282. Removed rigid scatterer, added tests
Refs #10282. Added occupancy to calculation, wrote test
Refs #10282. Added static create method
Refs #10282. Completed ScattererCollection and tests
Refs #10282. Renamed ScattererCollection
Refs #10282. Added documentation.
Merge branch 'feature/10282_create_scattering_function' into develop