Move revisionloader.py into core?

[Ian Clatworthy]

Jelmer Vernooij wrote:
> Hi Ian,
> 
> On my way to the airport this morning I had a look at how difficult it
> would be to use some of the speed improvements in bzr-fastimport in
> bzr-svn. RevisionLoader is really quite nice and generic so rather than
> maintaining a copy of it in bzr-fastimport I was wondering whether it
> would make sense to add it to bzrlib so it can be used by bzr-svn (and
> perhaps others?) directly. What do you think?

I think it's a good idea. It will need some test love first though.

Ian C.