[FFe] add support for 'cloud-archive:' like 'ppa:' but for cloud archive

I've just pushed to trunk, and uploaded to ubuntu saucy.

I've tested this like the following:
#fresh launch of saucy instance

sudo apt-get update --quiet
sudo apt-get install --assume-yes --quiet lxc
r=saucy
sudo lxc-create -n source-$r-amd64 -t ubuntu-cloud -- --release=$r --arch=amd64;

sudo lxc-clone --snapshot -B overlayfs -o source-$r-amd64 -n test1-$r; done

# inside
TEST_PPA="ppa:ubuntu-server-ec2-testing-dev/testing"

# add the ppa to get new version
sudo apt-add-repository -y ppa:smoser
sudo apt-get update -qy
sudo apt-get install -qy software-properties-common

# verify you're prompted for adding a ppa
# you should see a message with info about the ppa. hit ctrl-c.
# expect it is cancelled
sudo apt-add-repository $TEST_PPA

# add again, this time saying 'yes'
sudo apt-add-repository $TEST_PPA
sudo apt-get update
sudo apt-get install smello
sudo apt-get --purge remove smello

sudo apt-add-repository --remove $TEST_PPA
sudo apt-get update
# look for 'smello' (to verify archive removed)
# this should fail with 'Unable to locate package smello'
apt-cache policy smello

## verify '-y' works.
sudo apt-add-repository -y $TEST_PPA
sudo apt-get update

## verify cloud-archive: things work

# because this is saucy, and cloud archive not supported on saucy
# this should fail. Answer 'y' and then it should fail with
# a message
sudo apt-add-repository cloud-archive:havana

# override with CA_ALLOW_CODENAME
sudo CA_ALLOW_CODENAME=$(lsb_release -sc) apt-add-repository cloud-archive:havana
## This should fail, as the pocket added would be
## saucy-updates/havana which wont exist (precise-updates/havana)
sudo apt-get update

## fix that, and make sure update works. apt-get update should succeed
## with out any problems
sudo sed -i 's,saucy,precise,g' /etc/apt/sources.list.d/cloudarchive-havana.list
sudo apt-get update

## also you should now have the ubuntu-cloud-keyring package installed
dpkg-query --show ubuntu-cloud-keyring

## cleanup outside
sudo lxc-destroy -n test1-saucy

This makes sense to me from an FFe POV, and the diff looks sane. FFe granted.

This bug was fixed in the package software-properties - 0.92.27

---------------
software-properties (0.92.27) saucy; urgency=low

  * support adding cloud-archive repositories using syntax like
    cloud-archive:havana (LP: #1233486)
 -- Scott Moser <email address hidden> Sun, 06 Oct 2013 13:30:54 -0400

I uploaded the linked branch to 12.04 proposed yesterday, its sitting in queue:
https://launchpad.net/ubuntu/precise/+queue?queue_state=1&queue_text=software-properties

Hello Scott, or anyone else affected,

Accepted software-properties into precise-proposed. The package will build now and be available at http://launchpad.net/ubuntu/+source/software-properties/0.82.7.6 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested, and change the tag from verification-needed to verification-done. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed. In either case, details of your testing will help us make a better decision.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance!

Tagged verification done, heres a typescript showing that.

This bug was fixed in the package software-properties - 0.82.7.6

---------------
software-properties (0.82.7.6) precise-proposed; urgency=low

  * support adding cloud-archive repositories using syntax like
    cloud-archive:havana from add-apt-repository (LP: #1233486)
 -- Scott Moser <email address hidden> Tue, 08 Oct 2013 13:33:57 -0400

The verification of this Stable Release Update has completed successfully and the package has now been released to -updates. Subsequently, the Ubuntu Stable Release Updates Team is being unsubscribed and will not receive messages about this bug report. In the event that you encounter a regression using the package from -updates please report a new bug using ubuntu-bug and tag the bug report regression-update so we can easily find any regresssions.