support admin_email config and pass through into blocking errors, 

Merge branch 'neilj/update_limits_error_codes' of github.com:matrix-org/synapse into neilj/admin_email

combine mau metrics into one group

Don't fail requests to unbind 3pids for non supporting ID servers

Merge branch 'develop' of github.com:matrix-org/synapse into neilj/change_prometheus_mau_metric_name

Neil/fix postgres test initialise reserved users

Block ability to read via sync if mau limit exceeded

remove comments

Neilj/fix reap users in postgres

update docker base-image to alpine 3.8

Use recaptcha_ajax.js directly from Google

Revert "support admin_email config and pass through into blocking errors, return AuthError in all cases"

This reverts commit 0d43f991.

Blackify the tests