Merge pull request openedx#1742 from edx/pwnage101/cherry-pick-gdpr-s…

…tuff-into-hawthorn-docs

Cherry-pick GDPR stuff into hawthorn docs

Merge pull request openedx#1723 from edx/grantg/build-run

Creating a Hawthorn version of the Building & Running Guide

Merge pull request openedx#1713 from edx/pwnage101/fix-broken-reference

fix broken reference

Merge pull request openedx#1713 from edx/pwnage101/fix-broken-reference

fix broken reference

Merge pull request openedx#1713 from edx/pwnage101/fix-broken-reference

fix broken reference

Merge pull request openedx#1710 from edx/sylvia/DOC-3942

Small updates to About video and course rerun info

Merge pull request openedx#1558 from edx/grant/ginkgo

Grant/ginkgo

Merge pull request openedx#1488 from replaceafill/default_discussion_…

…topic

Added note for setting the default topic for new posts in the Discussion page

Merge pull request openedx#1488 from replaceafill/default_discussion_…

…topic

Added note for setting the default topic for new posts in the Discussion page

DOC-3634 Roll back to Sphinx v1.4.9

(cherry picked from commit 9e2cc24)