Further code cleanup

code cleanup

This cleans up the example code a little bit.
Fixed detector.export_data.
Generate diagram before performing analysis. If analysis fails,
a diagram is generated anyway.
Update various examples to use the aboe save function.

Fix clippy warnings.

added to_dot_test

not really useful yet...

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

Fixed tests for group. All tests pass again.

Remove example trait_test.
Doc fixes.