* Make the library modular usable.
* Put back removing qualified boostcpp tag. As we need it until the Jamroot removes the qualified tag.
* Switch to library requirements instead of source. As source puts extra source in install targets.
* Remove uses of BOOST_ROOT in Jamfiles.
* Add requires-b2 check to top-level build file.
* Bump B2 require to 5.2
* Update copyright dates.
* Move inter-lib dependencies to a project variable and into the build targets.
* Update build deps.
