switch to weave format

[Martin Pool]

I think we should make the weave (bzr.newformat) branch the main line
for new development.  It is not perfect yet, but a large improvement
over the previous format, and good enough that I think we can adopt it
as a development version.  Robert and I have merged the code from
bzr.dev and his bzr.integration into newformat, so it has all the
bugfixes that have been already integrated.  I think it is
feature-complete with everything previously mentioned.

The weave format and the inventory stored within it could be improved,
perhaps by going to an append-only weave, but I think it's better to
switch now and then do that work.

>From this point onwards I'd ask people to write any submissions
against the new format.  I will make a copy of the bzr.dev branch and
move the new format into bzr.dev, so by pulling from there you'll get
the new code.  You'll then need to upgrade any branches.

I'm going to keep bzr itself in the old format just for a few more
days and probably upgrade the branch around the end of this week. 
First of all I'm going to fix the bad branch/clone performance of the
new format and then merge some of the pending patches.

--
Martin