Avoid directory count limits in persistent_dict

Fix some markup fails in pytools.log

Placate flake8 quotes linter

Document log

See merge request !46

Table: add csv output

add github-flavored markdown and aligned output for Table

Co-authored-by: Andreas Klöckner <inform@tiker.net>

Doc fixes

See merge request !45

See https://docs.github.com/en/github/writing-on-github/organizing-information-with-tables
for specification

Topological ordering with priorities