bzr ppa updates

[Martin Pool]

I'm thinking of refactoring the ppas along the lines discussed a while
ago, and making use of the not-so-new feature of multiple ppas per
team.  In particular to insert a new "proposed" PPA where we can get
packages uploaded and built in that environment before making them
generally available.

  ~bzr/
     2.1 - current most stable build of code for 2.1 for all supported
distroseries
     2.1-proposed - pending uploads for 2.1; once we know they are not
broken they get copied to 2.1
     2.2 - similar
     2.2-proposed

We could make a new ~bzr-ppa team to own this which would avoid
bothering members of ~bzr who don't want to see ppa mail, but it would
be a more messy transition for users with ~bzr ppa urls configured
onto their machine.

I'm not sure if it's better for the ppa to be called "2.2" and "2.1"
specifically or just "beta" and "stable", and then perhaps version
numbers for older than the current stable release.
-- 
Martin