[MERGE] bzr.exe: move builtin plugins out of library.zip to directory 'plugins'

[Ian Clatworthy]

Ian Clatworthy wrote:
> Alexander Belchenko wrote:
>> This patch finishes reorganization of built-in plugins support for bzr.exe
>> that I started before bzr 1.0.
> 
>> Now builtin plugins resides in filesystem,
>> so user is able disable them, if needed.
> 
> Hooray for this bit in particular.

And another thing I forgot: this is definitely worthy of a NEWS entry as
it's an important change for Windows users.

Ian C.