Replace the use of the internal_report structure (for reports from
engines, MPV etc) with the Rose program interpreter.
SOM processing was reworked to use a new som_operation structure that is
embedded in the appropriate instructions.
This changes all the execute_graph() interfaces so that instead of
mutating a std::set of vertices, they accept an initial flat_set of
states and return a resultant flat_set of states after execution.
(Note that internally execute_graph() still uses bitsets)
This is both faster and more flexible.
