Add support for adding ppa's via aliases with a new ppa command

[Tim Lunn]

Add support for parsing a ppa from chroot alias. Also adds a new 'ppa' command to add/remove aliases from the config.

ProblemType: Bug
DistroRelease: Ubuntu 15.04
Package: sbuild-launchpad-chroot 0.7
ProcVersionSignature: Ubuntu 3.16.0-28.38-generic 3.16.7-ckt1
Uname: Linux 3.16.0-28-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 2.15.1-0ubuntu1
Architecture: amd64
CurrentDesktop: GNOME
Date: Fri Jan 9 12:46:30 2015
InstallationDate: Installed on 2012-09-23 (838 days ago)
InstallationMedia: Ubuntu GNOME Remix 12.10 "Quantal Quetzal" - Alpha amd64(20120922)
PackageArchitecture: all
SourcePackage: sbuild-launchpad-chroot
UpgradeStatus: No upgrade log present (probably fresh install)
modified.conffile..etc.schroot.setup.d.90apt.sources: [modified]
mtime.conffile..etc.schroot.setup.d.90apt.sources: 2015-01-09T11:20:10.851000

[Jeremy Bícha (jbicha)]

This can be done a bit less simply using the technique from
https://wiki.ubuntu.com/SimpleSbuild#Temporarily_adding_PPAs

Setup (using the GNOME3 Team PPA as example)
-----
gpg2 --keyserver keyserver.ubuntu.com --recv 9D542E3D52C801D9F8E31682F1773AF13B1510FD
gpg2 --export --armor 9D542E3D52C801D9F8E31682F1773AF13B1510FD > ~/gnome3-team.asc
gpg2 --delete-key 9D542E3D52C801D9F8E31682F1773AF13B1510FD

Build command (customize for your setup)
-------------
sbuild -A -d xenial-amd64 --extra-repository-key=/home/jeremy/gnome3-team.asc --extra-repository="deb http://ppa.launchpad.net/gnome3-team/gnome3-staging/ubuntu xenial main"

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.