add logistics for shared_ptr where necessary

Paul Gessinger authored 6 years ago and Andreas Salzburger committed 6 years ago

The corresponding "unit"-test is relatively bare-bones

[ignore-license]

changes to closeGeometry() for unique volume ID
adaption to MaterialMapping algorithm to create BinnedSurfaceMaterial

- GeometryObject factories now emit and request mutables, as before

- To ease "lazy construction", constructors now return MutableTrackingVolumePtr
- Remaining violations of constness are now clearly exposed as such
(const_casts, const_pointer_casts, "mutable"-prefixed variable naming)

- small adaptions to digitization & identifier
- serialiser for BinUtility

TODO -> todo
paramt -> tparam

some other minor fixes