Add MET end of event sequence

We want to add the MET algorithms to the end of event sequencer so that they are available on all output events.

@tamartin will want to review this to make sure I've not done anything really stupid and @bcarlson might want to make sure that I've not missed any algorithms we should be looking at.

When this is accepted this will significantly alter the monitoring output (as the algorithms will be run on every event) so @khamano and @chenb should be aware of it.