registry: make certain headers optional

For a pull-only, static registry, there only a couple of headers that
need to be optional (that are presently required.
* X-Docker-Registry-Version
* X-Docker-Size
* X-Docker-Endpoints

Docker-DCO-1.1-Signed-off-by: Vincent Batts <vbatts@redhat.com> (github: vbatts)
registry: Info collection

roll version and standalone information into the _ping. And to support
Headers they are checked after the JSON is loaded (if there is anything
to load). To stay backwards compatible, if the _ping contents are not
able to unmarshal to RegistryInfo, do not stop, but continue with the
same behavior.

Docker-DCO-1.1-Signed-off-by: Vincent Batts <vbatts@redhat.com> (github: vbatts)
Use apparmor_parser directly

The current load script does alot of things.  If it does not find the
parser loaded on the system it will just exit 0 and not load the
profile.  We think it should fail loudly if it cannot load the profile
and apparmor is enabled on the system.
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Move apparmor to top level pkg
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Ignore is not exist error
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Generate imports based on what is avaliable
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
This permission should be interpreted as octal, not decimal

Docker-DCO-1.1-Signed-off-by: Kato Kazuyoshi <kato.kazuyoshi@gmail.com> (github: kzys)
SQLite is also available in FreeBSD

Docker-DCO-1.1-Signed-off-by: Kato Kazuyoshi <kato.kazuyoshi@gmail.com> (github: kzys)
Added support for multiple endpoints in X-Docker-Endpoints header
Docker-DCO-1.1-Signed-off-by: Joffrey F <joffrey@docker.com> (github: shin-)
Refactor cgroups file locations
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Move systemd code into pkg
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Move raw cgroups into fs package (filesystem)
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Break down groups into subsystems
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Add remove method to subsystems
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
typo fix: 'methid' -> 'method'
Add missing blank lines in between list items

Lists with paragraphs as items need blank lines in between
items to generate correct layout.

Docker-DCO-1.1-Signed-off-by: Lance Chen <cyen0312@gmail.com> (github: Lance0312)
Squashed commit of the following:

commit 75af1649b063abbc5d662fd2f8bc4ff62c927687
Author: Evan Hazlett <ejhazlett@gmail.com>
Date:   Sun Apr 20 01:32:42 2014 -0400

    more refactor

commit 43b36d0f15d634497127bcb17dacaa70ae92e903
Author: Evan Hazlett <ejhazlett@gmail.com>
Date:   Sun Apr 20 01:11:49 2014 -0400

    refactored cgroup param parsing to util func

commit e3738b0168a075bd92ec828879b0e46bdbbe3845
Author: Evan Hazlett <ejhazlett@gmail.com>
Date:   Sun Apr 20 00:57:19 2014 -0400

    dat error checking

commit 57872bcc59403ecd308cfe97c78f73d6ca58d165
Author: Evan Hazlett <ejhazlett@gmail.com>
Date:   Sun Apr 20 00:43:25 2014 -0400

    proper use of fmt.Errorf

commit 43dad6acc0cb21aac2b04ce074699879898ee820
Author: Evan Hazlett <ejhazlett@gmail.com>
Date:   Sun Apr 20 00:36:45 2014 -0400

    proper placement of defer

commit b7f20b934b2bc92cd39397dbc608b77bff28493c
Author: Evan Hazlett <ejhazlett@gmail.com>
Date:   Sun Apr 20 00:34:39 2014 -0400

    defers, error checking, panic avoidance

commit 7a9a6ff267f8806dfe6676486f73fe89b72968fb
Author: Evan Hazlett <ejhazlett@gmail.com>
Date:   Sun Apr 20 00:22:00 2014 -0400

    data param to use container info instead of host

commit 0e0cf7309be1644687160d6519db792b23cd26e9
Author: Evan Hazlett <ejhazlett@gmail.com>
Date:   Sun Apr 20 00:11:29 2014 -0400

    added stats for cpuacct, memory, and blkio

Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Refactor stats and add them to all subsystems
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Add external function to get cgroup stats
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Fix parsing of blkio files
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)