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>
There's one "container" too many here.

I think "`AND` only when" can simply be "`AND` the event type is.."

It looks like you're using back ticks to *emphasize* the AND / OR. Because this is not literal output or code, I think they should be *and* in stead of `AND` (Fred?)