Adam Helps authored Feb 27, 2020 and Martin Marinov committed Feb 27, 2020

* Adds optional pre-call and post-call events in the journal to implement reference count abridgement.
* Adds new documentation for many functions, and improves existing.
* Removes "JOURNAL_FUNCTION" from the created macros when journal is turned off, because there is no such macro when journal is turned on.
* Adds the ability to unlink names in the journal manually. This was already being done by destructors, but there wasn't a way to do it for names managed in other ways.
* Add HandleT<> to support handle tracking
* Generalize the key<> function to handles and make key a pair of size_t 
* Simplify ReturnLink and make it work for HandleT<>
* Adds an operator< to the HandleT class so that it can be used as a key in associative containers (T-Splines uses it this way for ref-count collapsing).