help/config: expand [subpaths] help
Brifly explain why rewriting subrepository paths can be necessary.
Explain that relative subrepository paths are made absolute before
rewrite rules are applied.
doc: update copyright years to 2012
I sometimes look at a piece of software and if the man page says
"Copyright 2004", then I'm inclined to think that the project is stale
or that the authors are lazy. Neither is good publicity for us :-)