Resolve "Simulate SFG"

Closes #22 (closed) and #24 (closed). This merge will:

• add some important test cases
• implement deep copying of SFG
• implement Simulation
• add Register operation
• refactor operation evaluation to allow for simulation of registers/delays with loops and nested SFGs
• refactor neighbors/parameter/traverse interface by moving it to GraphComponent
• add some convenience functions to Operation
• tidy up the method signatures of some interfaces to be more general
• move bit length specification from InputPort to Signal
• add customization point for specifying input truncation behavior for user operations