Add global option --root=dir to specify location of .bzr

[Jari Aalto]

Currently the project has one root:

    $ cd project
    $ bzr init         
    
I'd like to propose an option --root which would specify the location
of the root directry of the repository, so that the above woul dbe
effectively same as:

    $ cd project
    $ bzr --root=.bzr init         

The new option would also allow overlaying several roots to the same
project:

For the "standard publish"

    $ cd project                                    [1]
    $ bzr init         

For the "developer-only files"

    $ cd project                                    [2]
    $ bzr --root=.bzr-dev init         

The idea behind this is to separate publishable files from the
developers own files which still need to be versioned properly:

    $ bzr add file.c file.h Makefile                [1]
      ...

    $ bzr root=.bzr-dev add mychecker.sh scp.sh     [2]
      ...

When it comes time to publish, only the [1] is pushed to the server
and the developer continues to have [2] in his private space. Those
might be programs that help him in his work, but which are not
genrally useful to anyone else outside of his environment.

Jari