create c++ API

[lizutah]

replace current main (BP.cpp) with calls to new API so that the command line tools still works (even if it's working in a python script).

[erikjensen]

There is now a very basic API providing the same functionality as is available on the command line. However, a lot more work needs to be done in order to make PB-AM usable as a library. See issue #7 for more information on the necessary improvements.