Merge pull request #397 from marineam/btrfs

feat(coreos-base/coreos): Add btrfs-progs and brctl
feat(app-emulation/docker): Add .network configs for networkd

These will match docker0 and the assorted veth* interfaces before the
default dhcp enabled network config does so networkd leaves them alone.
fix(sys-apps/baselayout): Create resolv.conf symlink except in SDK

networkd uses its own location for generating resolv.conf and a new
tmpfiles rule creates a symlink to it in both -generic and -usr images.
This is not applicable to SDK so remove the rule in that case.
fix(coreos-init): Add rdepend on coreos-cloudinit
Merge pull request #398 from marineam/network

networkd configuration
bump(coretest): Use latest coretest

commit 03512eea351cd7903b070b4969c1dd764a27928b
Merge pull request #399 from bcwaldon/add-cloudinit

Add init rdepend; update coretest
fix(sys-apps/baselayout): Bump to include resolv.conf tmpfiles config.
Merge pull request #400 from marineam/network

fix(sys-apps/baselayout): Bump to include resolv.conf tmpfiles config.
bump(coreos-base/coreos-init): Enable btrfs resizing on boot.
bump(coreos-base/vboot_reference): New cgpt version

Tolerates btrfs, better protective MBR support and adds hybrid MBR support.
bump(sys-kernel/bootengine): drop resize module

Moving to btrfs means we don't need to resize before mounting.