Improved handling of headers in relation to precompilation.
Created CMake test that builds and runs all unit tests.
Added DocSet generation to Doxygen.
Removed UnitTest++ dependency; increased minimum CMake version to newest.

Changed to Boost.Test for unit testing.  Increased the minimum CMake version to the newest because this is the version tested; if an earlier version must be used, the cmake_minimum_required call in the CMakeLists.txt file can be modified as necessary.