branch specific rules - the latest proposal

[Ian Clatworthy]

I spoke to Martin yesterday about this and our proposal is to store 
branch specific rules in .bzrmeta/rules. This file will be versioned.

Some other important details:

* The .bzrmeta directory will be the recommended place for plugins
   to store "in tree metadata".

* Content filters will not be applied to files in that directory.

* If conflicts exist in .bzrmeta/xxxxx after a merge, the base
   content will be used. Otherwise, the in-tree content will be used.

There will undoubtedly be more devil in the detail but that's the 
direction we're thinking of currently.

We'll discuss this further today with interested parties (Robert, Aaron, 
John, etc.). If anyone on the list likes or dislikes the above, please 
speak up.

Ian C.