[MERGE] Content filtering + EOL, keywords plugins

[Martin Pool]

Martin Pool has voted resubmit.
Status is now: Resubmit
Comment:
> We still have some disagreement on whether this requires a format
> bump or not. Martin and I think not, Robert thinks otherwise. I'll
> let Robert and Martin argue that out because I lack the energy to
> go over the issue yet again.

So, we did, and I agree we should stick with adding new formats when 
changing behaviour.  The bulk of this code is not tied to that decision, 
but I think that it does implicitly turn it on for all working trees, 
and we don't want that.  If we cut that out (and possibly do it in a 
plugin), I'd be ok to merge this.

For details, see: 
http://bundlebuggy.aaronbentley.com/project/bzr/request/%3C4880CF60.2080805%40canonical.com%3E
Project: Bazaar