Websocket logging

We want to collect logging data from the web browser and store it in case the
operator needs it later.

The GUI already takes advantage of the Zaqar messaging system which transfers
messages between the server and the client via websockets. We can use this to
send logging messages to the server. We can create a new Zaqar queue called
*tripleo-logging* and send everything there.

The javascript application should send any useful information to the server, for
example:

* redux action messages
* exception tracebacks
* useful console.log calls
* route changes

As part of the implementation of this feature, we could

* register a global *onerror* handler which catches all exceptions, logs them
  and re-raises the original exception (this is what the sentry javascript
  client does)
* monkey-patch the *console.** functions (log, warn, debug, etc) to use the new
  logging mechanism
* convert all immutable.js data structures to plain javascript before sending

On the other side of the Zaqar queue, we shall create a simple Python script
which will be run periodically by a cronjob. This script will drain the Zaqar
queue and append the messages to a log file on disk. We can then create an
httpd vhost which would allow the client to retrieve this log file and make it
available to the user for viewing.