* Make the library modular usable.
* Switch to library requirements instead of source. As source puts extra source in install targets.
* Update library dependencies.
* Add requires-b2 check to top-level build file.
* Bump B2 require to 5.2
* Change all <source> references to <library>.
* Move inter-lib dependencies to a project variable and into the build targets.
* Switch to /boost/test//included target for header only mode of Boost.Test.
* Update build deps.
* Change math dep real target math/tr1.
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