Add config for new plainbox-provider-phablet and files to provision utopic

The tarmac config file addition is very straightforward.

debootstrap on Ubuntu 14.04 does not know about utopic, but all the ubuntu scripts are simple symlinks to gutsy; this code also checks and adds a symlink for utopic, so we can deploy and test that release. This is done when redeploying the juju charm, I did it that way so I don't have to force a full redeployment.