Merge lp://staging/~mbp/bzr/135234-checkout-relpath into lp://staging/bzr

3 cheers for this patch! Some minor things:

* there's a bit of junk in NEWS - "* Cope"
* builtins.py has ", e" added to an except clause and the exception isn't used anywhere. (I'm fine with leaving that as is though - it's harmless.)

Fed to pqm

star-merge http://bazaar.launchpad.net/~mbp/bzr/135234-checkout-relpath http://bazaar.launchpad.net/~bzr-pqm/bzr/bzr.dev

Fed to pqm

star-merge http://bazaar.launchpad.net/~mbp/bzr/135234-checkout-relpath http://bazaar.launchpad.net/~bzr-pqm/bzr/bzr.dev

fails in an info test:

 File "/home/pqm/bzr-pqm-workdir/home/+trunk/bzrlib/tests/blackbox/test_info.py", line 1210, in assertCheckoutStatusOutput
   ), out)
AssertionError: texts not equal:
 Lightweight checkout (format: 2a)
 Location:
   light checkout root: tree/lightcheckout
         checkout root: tree/checkout
- checkout of branch: repo/branch
+ checkout of branch: ../../repo/branch/
? ++++++ +

 Format:

Aaron raises a question in https://bugs.edge.launchpad.net/bzr/+bug/135234/comments/4 as to whether it's really ideal to store relative paths all the time.

We do as a general principle store relative paths when possible, partly because they're more likely to work when the same directories are addressed across different transports.

I think the frequency of relative paths is increasing as more people use Neil's colo plugin and the various workspace models in Explorer. We could detect those cases pretty easily I suspect, e.g. we want relative paths in at least these cases:

1. If the branch path starts with the checkout path
2. If the checkout path starts with the repository path.