Update docs building, cleanup
Update docs building and cleanup a bit:
* Update requirements for Sphinx and openstackdocstheme for
python 3, create doc/requirements.txt for these
* Remove unneeded doc and translation sections from setup.cfg
* Remove install_command, it's unneeded, the default is fine,
move constraints into deps, use TOX_CONSTRAINTS instead of
obsolete UPPER_CONSTRAINTS
* Use new variables from updated openstackdocstheme
Change-Id: I659a8736195ff621032b4fb3bd7a72fa616cf8c6
6 files changed