Add event logging to libpod, even display to podman

In lipod, we now log major events that occurr.  These events
can be displayed using the `podman events` command. Each
event contains:

* Type (container, image, volume, pod...)
* Status (create, rm, stop, kill, ....)
* Timestamp in RFC3339Nano format
* Name (if applicable)
* Image (if applicable)

The format of the event and the varlink endpoint are to not
be considered stable until cockpit has done its enablement.

Signed-off-by: baude <bbaude@redhat.com>

cmd/podman/main.go

@@ -36,6 +36,7 @@ var (
 // implemented.
 var mainCommands = []*cobra.Command{
 	_buildCommand,
+	_eventsCommand,
 	_exportCommand,
 	_historyCommand,
 	&_imagesCommand,