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

Various code cleanups.

Use OpmResult defined in error module.

Scenery::connect_nodes return () instead of EdgeIndex since it's not
needed anaywhere.

Fixed tests for group. All tests pass again.

This forces the usage of the "new" function to submit a name.

Update examples accordingly

Separate Dottable trait to additional file.

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.

Fix some doc errors.

Add example src-detector.

Add port information for NodeDummy & NodeBeamSplitter