A function that returns a nested list which describes the precedence of all of the output ports in an sfg. Output ports with different dependencies are handled correctly.
A function that returns all components of a specified type_name in an sfg.
Test cases covering both of above.
Removal of the old precedence_graph and schema files.
Updated class diagram with new precedence_graph functions.
The inputs_required_for_output() implementation for SFG is now iterative and is nolonger is recursive.