controllers: consistently use c.cs_comments and cs_statuses c.comments and c.statuses were also used for lists of comments and statuses. To get more consistency and avoid confusion and conflicts, use different for names for mappings from changeset hashes.

# requirements.txt file for use as "pip install -r requirements.txt" as a
# readthedocs compatible alternative to "pip install -e ." which is a working
# alternative to "setup.py develop" which doesn't work with Mercurial 3.7
.