Add links in docs to glossary

[jessica-mitchell]

This PR adds the hover tooltip reference role to glossary terms throughout the documentation (see #2109).

[github-actions[bot]]

Pull request automatically marked stale!

[terhorstd]

This seems ready to review, but recently got some conflicts.

[jessica-mitchell]

ping @med-ayssar!

[heplesser]

@med-ayssar Ping!

[med-ayssar]

I would apply:

.. code-block:: C++

   inline void
   nest::Stopwatch::print( const char* msg, timeunit_t timeunit, std::ostream& os ) const
   {
     // code
   }

For the block starting at L233

[jessica-mitchell]

@med-ayssar I think all issues are resolved now

[jessica-mitchell]

@med-ayssar can you do a final review or if you're satisfied approve? thanks!

[med-ayssar]

Looks good

[heplesser]

Pure documentation change, therefore merging based on single review and in spite of full test failing for unrelated reasons.