[boost] New getting started guide

I've got a first draft of the new getting started guide ready (enclosed). Comments would be appreciated. I plan to factor it out into separate documents, e.g. one just for *nix, one just for Visual Studio, etc., which should help make it more coherent... but I need to do a small amount of tool writing before I can accomplish that without duplicating information. The source file is checked in at more/getting_started.rst -- Dave Abrahams Boost Consulting www.boost-consulting.com