Add stack-docs lsstcc command
Add stack-docs lsstcc command

This command line subcommand lets users list the available API names in
the Doxygen tag file. By default, they are escaped so that they're
immediately copy-and-pastable as content for the lsstcc role.

lsst-sqre/documenteer,lsst-sqre/documenteer,lsst-sqre/sphinxkit