Further testing needed.

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

Update dependent code accordingly.

Update examples & tests accordingly.

Add name parameter to IdealFIlter::new

Fixed missing inverted() fn.

code cleanup

Various code cleanups.

Use OpmResult defined in error module.

Add general OpmResult typedef to error module.

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.