Add unit tests to OpticGraph.
Add unit tests to OpticRef.

Update dependent code accordingly.

Use OpmResult defined in error module.

Add general OpmResult typedef to error module.

Fix clippy warnings.

Copied from EnergyMeter. Needs modifications yet.

Update docs. Update filter_test example.

This simply forwards incoming LightResult.
Rename RefNode::new -> RefNode::from_node to fix clippy warnings.

Function was completely rewritten. Fixed many clippy warnings and
reformatted code.

not yet tested.

Fix some doc errors.

Add port information for NodeDummy & NodeBeamSplitter