Re-write virsh console to use streams

Re-write virsh console to use streams

This re-writes the 'virsh console' command so that it uses
the new streams API. This lets it run remotely and/or as a
non-root user. This requires that virsh be linked against
the simple event loop from libvirtd in daemon/event.c
As an added bonus, it can now connect to any console device,
not just the first one.

* tools/Makefile.am: Link to event.c
* tools/console.c, tools/console.h: Rewrite to use the
  virDomainOpenConsole() APIs with streams
* tools/virsh.c: Support choosing the console name
  via --devname $NAME