Update & extend unit tests accordingly.

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