It's been pointed out that DEBUG logs could contain sensitive
information (access tokens, etc.), which makes them unsuitable
for sharing with others. INFO should be enough.

Clarify sentence about dedicated user for access token

Also discussed previously in #213 (Github Pull Request).

shared-secret-auth and rest-auth logging is still at `INFO`
intentionally, as user login events seem more important to keep.
Those modules typically don't spam as much.

We recently had someone in the support room who set it to `false`
and the playbook ran without any issues.

This currently seems to yield the same result as 'none', but it's
better to avoid such behavior.

Refer to 524436ebef and #230 (Github Issue).

Fixes #230 (Github Issue).

Related to https://github.com/Half-Shot/matrix-appservice-discord/issues/510

It adds support for a new `DISABLE_SENDER_VERIFICATION` environment
variable that can be used to disable verification of sender addresses.

It doesn't matter for us, but we upgrade to keep up with latest.

Fix apt message: docker doesn't support arch 'i386'

Related to #223 (Github Pull Request)

Update synapse (1.1.0 -> 1.2.0)

Update nginx (1.17.1 -> 1.17.2)

Upgrade riot-web (1.2.4 - 1.3.0)

introduce configuration to change riot branding / title

Looks like these client ids are actually integers,
but unless we pass them as a string, the bridge would complain with
an error like:

    {"field":"data.auth.clientID","message":"is the wrong type","value":123456789012345678,"type":"string","schemaPath":["properties","auth","properties","clientID"]}

Explicitly-casting to a string should fix the problem.

The Discord bridge should probably be improved to handle both ints and
strings though.

Fixes #216 (Github Issue).

Update to riot 1.2.3

We do restart Synapse explicitly, but some other services
(bridges, matrix-corporal, ..) may not restart sometimes.

It's best to restart all services explicitly.

Regression since 174a6fcd1b3, #204 (Github Pull Request),
which only affects new servers.

Old servers which had their passkey.pem file relocated were okay.

Bump nginx version to 1.17.1