Events filtering (daemon side)

When you have tons of containers on your host, events can be hard to read.

Here is a proposal to add some filters to `docker events`
In this 1st version: `image`, `container` and `event`

In the futur, we *might* move `--since` and `--until` into the filters.

See the doc for some examples.

Signed-off-by: Victor Vieux <vieux@docker.com>
events both will be displayed, all the others are filtered.

I'm not sure this whole conversation should happen here, we have  filters in docker ps for months; you can filter multiple exit status at the time using the same mechanism