filters, for images: start with untagged/tagged boolean

This is a new feature and flag. (replaces the suggestion of a flag for
--untagged images).
The concept is to have a syntax to filter. This begins with this
filtering for the 'images' subcommand, and at that only filtering for
whether images are untagged.
  example like: docker rmi $(docker images -q --filter 'untagged=true')

Docker-DCO-1.1-Signed-off-by: Vincent Batts <vbatts@redhat.com> (github: vbatts)
filters: remove out filter proc prototype

Docker-DCO-1.1-Signed-off-by: Vincent Batts <vbatts@redhat.com> (github: vbatts)
filters, for images: docs

Docker-DCO-1.1-Signed-off-by: Vincent Batts <vbatts@redhat.com> (github: vbatts)
filters: cleanup & fmt

Docker-DCO-1.1-Signed-off-by: Vincent Batts <vbatts@redhat.com> (github: vbatts)
images filter: remove the redundant inverted filter

Docker-DCO-1.1-Signed-off-by: Vincent Batts <vbatts@redhat.com> (github: vbatts)
images: fix markdown documentation

Docker-DCO-1.1-Signed-off-by: Vincent Batts <vbatts@redhat.com> (github: vbatts)
filter flag: split out for separate --filter flags

adding tests and allowing for easy passing of filters.Args from client
to server.

Docker-DCO-1.1-Signed-off-by: Vincent Batts <vbatts@redhat.com> (github: vbatts)
server: very debug.

Docker-DCO-1.1-Signed-off-by: Vincent Batts <vbatts@redhat.com> (github: vbatts)
filters: change untagged to dangling

Docker-DCO-1.1-Signed-off-by: Vincent Batts <vbatts@redhat.com> (github: vbatts)
filters: use json marshal, instead of beam/data

Docker-DCO-1.1-Signed-off-by: Vincent Batts <vbatts@redhat.com> (github: vbatts)
filters: don't encode an empty set. update comments

Docker-DCO-1.1-Signed-off-by: Vincent Batts <vbatts@redhat.com> (github: vbatts)
grammar; nothing big

Docker-DCO-1.1-Signed-off-by: Zac Dover <zdover@redhat.com> (github: zdover23)

Added another "The"

Docker-DCO-1.1-Signed-off-by: Zac Dover <zdover@redhat.com> (github: zdover23)
libcontainer/cgroup: Use raw access to set up and join the devices cgroup

The systemd support for the devices cgroup lacks two required features:
 * Support for wildcards to allow mknod on any device
 * Support for wildcards to allow /dev/pts support

The second is available in more recent systemd as "char-pts", but not in e.g. v208 which is in wide use.

Additionally, the current approach of letting systemd set up the devices cgroup and then adding
some devices to it doesn't work, because some times systemd (at least v208) re-initializes
the devices cgroup, overwriting our custom devices. See https://github.com/dotcloud/docker/issues/6009
for the details.

When wildcarded mknod support is available in systemd we should implement a pure systemd version,
but we need to keep the old one around for backwards compat.

Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson)
filters: don't encode empty set. API docs

Docker-DCO-1.1-Signed-off-by: Vincent Batts <vbatts@redhat.com> (github: vbatts)
Merge pull request #4430 from vbatts/vbatts-images_orphan

Adding -f untagged=true flag to `docker images`
Merge pull request #6175 from alexlarsson/systemd-use-raw-devices

libcontainer/cgroup: Use raw access to set up and join the devices cgroup
Merge pull request #6173 from zdover23/03_Jun_2014

grammar; nothing big (added a "the")