const correctness flawed due to shared_ptr/unique_ptr usage

[neiser]

The main data structure ant::TEvent and ant::TEventData use std::unique_ptr and std::shared_ptr for the rather complex inter-event data dependencies (for example, particles point to their candidate they were made of, etc.). However, the const-ness of the TEvent given to physics classes does not apply to the objects managed as shared_ptr. So users can change events in physics classes, and influencing other physics classes unknowingly. That's a huge design flaw...

Likewise, the ant::Tree structure is also not const correctly implemented.

Creating some cc_shared_ptr which transfers its own constness to the managed object could be a nice solution. But implementation is far from being trivial (see branch cc_shared).