avoid use of /dev/disk/by-id in VirtualBox

/dev/disk/by-id is not stable in VirtualBox so we don't want to rely on
it.
Merge pull request #203 from aspiers/virtualbox-disk-by-id

avoid use of /dev/disk/by-id in VirtualBox
Add optional crowbar-applied boolean attribute to schema

Set it to false by default in the json and update proposal schema
version to 3.
Merge branch 'release/roxy/master' into merge-roxy
Merge pull request #213 from bkutil/add_applied_attribute

Add applied attribute
Merge pull request #214 from vuntz/merge-roxy

Merge roxy branch into master
Simplified/fixed UEFI config (bnc#865871)

I have simplified the UEFI configuration in order to get the
installation on UEFI hardware running. I extracted the UEFI informations
into an ohai plugin. This fixes
https://bugzilla.novell.com/show_bug.cgi?id=865871
Merge pull request #216 from tboerger/feature/uefi-fix

Simplified/fixed UEFI config (bnc#865871)
by-path links for virtio disk might not exist

Newer udev releases (e.g. on SLE 12) don't create the by-path links anymore for
virtio disks. Additionally they are not stable according to:
https://www.mail-archive.com/systemd-devel@lists.freedesktop.org/msg20607.html
Avoid using them for all platforms newer than what we currently support. Keep
the old behavior intact on currently supported platforms for backwards
compatibility.
Merge pull request #220 from rhafer/sle-12-virtio

Workaround missing by-path links for virtio disk
set the attribute value (otherwise node attributes are read-only)
Merge pull request #221 from jsuchome/sle12_update

set the attribute value (otherwise node attributes are read-only)
Remove trailing white space
Add helper for enabling or disabling tx offloading
Merge pull request #222 from dirkmueller/master

Add helper for enabling or disabling tx offloading