Several changes to 3D and 2D detector

[euryalus]

1. Added a loss function to the sphere optimization in order to increase robustness with outliers. The loss scale (0.01) was optimized to make standard deviations of sphere positions minimal.
2. In the 2D-detector made sure that in the end, really the best candidate is chosen and not just the last of all candidates that gets over the threshold set by final_perimeter_ratio_range_min.
3. In the 2D-detector, approximate paths of candidate ellipses are resolved to polylines before they are compared. Also, not all raw_edges are used to determine the ellipse support, but only the edges from the respective polyline.
4. In the 2D-detector, the final goodness of the fit is calculated on the the very final fit of the ellipse and also based on final_edges, instead of on all the raw_edges.
5. In the 2D-detector, the goodness of an ellipse fit now is also proportional to a factor depending on the ratio between support edges and all edges used in the fit. The ratio is exponentiated with an exponent larger 1.0, in order to make it harder for an ellipse fit to have very high confidence. This is also implemented in the string prior case.
6. Added a field to Detector2DProperties to set support_pixel_ratio_exponent, used in the calculation of the goodness of a fit. Setting this to a value larger 1.0, makes it harder for an ellipse to have a very high confidence. Setting it to zero, recovers the former way of calculating the goodness.