Shuffled around #include dependencies to allow the control algorithm diagram to be generated without copying code out of control_algorithm.c

Added ability to get/set PID constants. Passes regression tests, and is backwards-compatible. Does not support setpoints, because they will be set via a different interface

Resets recursively, keeping track of children. Created tests, which pass. Computation terminates on graph cycles. Added comments.

Some refactoring, separating node type from node instance. Added parameters, and disabled ability to set inputs.