[RFC] Take the all-in-one windows installer out of bzr core

[Ian Clatworthy]

Similar to what we do for OS X and Linux/UNIX distros, I think the
details of how we build the all-in-one Windows installer and what we put
in it ought to be taken out of the core. Technically, it doesn't make
sense for the core to know about what plugins and what versions of each
are bundled with it on each and every platform. Practically, I guess it
hasn't been a major problem in the past when we were shipping every
month but we won't be going forward.

Any objections?

Ian C.