Merge remote-tracking branch 'origin/references'
Adds columns `slogan' and `histrmk' to database
Code for slogans and historical remarks in tags/tex.py

Duplicates all code for `references' to `slogans' and `historical remarks'
Adds slogan and histrmk to list_of_standard_envs
Adds sql code for the slogans table
Merge branch 'master' of https://github.com/jcommelin/stacks-tools
Merge branch 'master' of https://github.com/stacks/stacks-tools