Merge branch 'release-v0.17.0' of github.com:matrix-org/synapse

CHANGES.rst

MANIFEST.in

README.rst

UPGRADE.rst

docs/admin_api/README.rst

docs/admin_api/purge_history_api.rst

docs/admin_api/purge_remote_media.rst

docs/code_style.rst

docs/turn-howto.rst

jenkins-dendron-postgres.sh

jenkins-postgres.sh

jenkins-sqlite.sh

jenkins-unittests.sh

jenkins/clone.sh

jenkins/prepare_synapse.sh

res/templates/notif_mail.html

scripts-dev/federation_client.py

scripts/hash_password

scripts/register_new_matrix_user

scripts/synapse_port_db