[MERGE] Document the change in the command lines use of MutablelTree and bump the API minimum version.

[Bundle Buggy]

Bundle Buggy has detected this merge request.

For details, see: 
http://bundlebuggy.aaronbentley.com/project/bzr/request/%3C1217889775.21489.68.camel%40lifeless-64%3E
Project: Bazaar