Do not drop sys_boot

This fixes #2391
Utils: Add ShellQuoteArguments
lxc: Work around lxc-start need for private mounts

lxc-start requires / to be mounted private, otherwise the changes
it does inside the container (both mounts and unmounts) will propagate
out to the host.

We work around this by starting up lxc-start in its own namespace where
we set / to rshared.

Unfortunately go can't really execute any code between clone and exec,
so we can't do this in a nice way. Instead we have a horrible hack that
use the unshare command, the shell and the mount command...
Add warning about SYS_BOOT capability with pre-3.4 kernels and pre-0.8 LXC.
Updated documentation footer to say "Docker Inc." instead of dotCloud. And added link to Read the Docs for giving them credit to hosting us. (Thanks Read The Docs!)
Clean up sphinx syntax, upgrade http markup package, minor link changes, update intro.
Merge pull request #2688 from dhrp/doc-layout-dotcloud-to-docker-inc

Updated documentation footer to say "Docker Inc." instead of dotCloud. And added Read the Docs.
Improvise documentation for builder.rst / VOLUME command
thankyou @tomdz - I forgot about URL based ADDs
Merge pull request #2691 from SvenDowideit/add-instruction-path-limitations

except URL-based ADDs
Merge pull request #2445 from alexlarsson/fix-shared-root-from-dm

Fix lxc start for shared root filesystems
Fix the brittle errorstring-to-httperror recognition code which in turn is required by autopull (the client issues a pull if container creation returns 404)
Merge pull request #2704 from shykes/fix-auto-pull

Fix the brittle errorstring-to-httperror recognition code
Merge pull request #2690 from codevin/master

Improvise documentation for builder.rst / VOLUME command
Merge pull request #1 from jpetazzo/2392-add-kernel-docs

Add warning about SYS_BOOT capability with pre-3.4 kernels and pre-0.8 LXC.
Merge pull request #2712 from makinacorpus/master

Do not drop sys_boot
Merge pull request #2689 from metalivedev/fix-syntax

Clean up sphinx syntax