Handle messages concurrently

[adamralph]

The V6 upgrade exposed the fact that the endpoints are currently not designed to handle messages concurrently.

Some of the problems:

• The projectors (as currently designed) must update the views in serial to avoid a last-in-wins scenario while two messages are being concurrently handled.
• The Twitter analyzer writes multiple lines to the console when handling each message, and these become interleaved when handling messages concurrently

There could be other issues too.

Note, as part of this, we should probably drop the use of ColoredConsole, since it does nasty locks around writing the console. We should be able to switch to using ANSI colour codes instead.