Disable responding with canonical json for federation

Turn use_frozen_events off by default

Only re-sign our own events

Fix ``KeyError: 'msgtype'``. Use ``.get``

Fixes a key error where the mailer tried to get the ``msgtype`` of an
event that was missing a ``msgtype``.

```
 File "synapse/push/mailer.py", line 264, in get_notif_vars
 File "synapse/push/mailer.py", line 285, in get_message_vars
 File ".../frozendict/__init__.py", line 10, in __getitem__
    return self.__dict[key]
    KeyError: 'msgtype'
```

Inline the synchrotron and pusher configs into the main config

This means that the workers can override the event_cache_size
directly without clobbering the value in the main synapse config.

Fix TypeError in call to bcrypt.hashpw

Fix some `/preview_url` explosions

- At the very least, this TypeError caused logins to fail on my own
  running instance of Synapse, and the simple (explicit) UTF-8
  conversion resolved login errors for me.

Signed-off-by: Salvatore LaMendola <salvatore.lamendola@gmail.com>

Enable testing the synchrotron on jenkins

Linearize fetching of gaps on incoming events

This potentially stops the server from doing multiple requests for the
same data.

Work around TLS bug in twisted

Correctly mark backfilled events as backfilled

Wrap up twisted's FileBodyProducer to work around
https://twistedmatrix.com/trac/ticket/8473. Hopefully this fixes
https://matrix.org/jira/browse/SYN-700.

Make get_domain_from_id throw SynapseError on invalid ID

Change /bin/bash to /bin/sh in tox.ini

No features of Bash are used here, so using /bin/sh makes it more portable to systems that don't have Bash natively (like BSD systems).

Add function to load config without generating it