* Overhaul of dealing with CMake use cases
* Put target property setup into a function
* Fix test standalone_with_boost for CMake
* Other minor fixes/edits
When building outside of boost, boost_json now supports the install option of cmake.
This patch produces a full, correct install which obeys CMAKE_INSTALL_PREFIX and
creates the correct config.cmake files in order to construct the target Boost::json
This config will automatically find Boost::system using the standard cmake find_package
command