switch kiwi appliance to use systemsmanagement:crowbar:2.0:staging OBS project

Since this appliance is primarily for development, it makes more sense
to consume packages from the systemsmanagement:crowbar:2.0:staging OBS
project first, and from systemsmanagement:crowbar:2.0 second.
Changed /usr/sbin/chroot to plain chroot.
Merge pull request #1719 from aspiers/topic/kiwi-staging-repo

switch kiwi appliance to use systemsmanagement:crowbar:2.0:staging OBS p...
change uses of throw to raise

'throw' is for escaping from control flow, whereas 'raise' is for
error conditions, e.g.

http://rubylearning.com/blog/2011/07/12/throw-catch-raise-rescue-im-so-confused/
Merge pull request #1718 from aspiers/topic/use-raise-not-throw

change uses of throw to raise