Implement cross-section area error analysis

[ChRen95]

Implementation of cross-section-area (cross-section-filling-ratio).
This improves the general capabilities of analyzing given pass designs.

[axtimhaus]

• Introduced target values of width and cross-section which default to usable width/cross-section. Can be given to set the reference for error values.
• Introduced cross section filling ratio.
• Introduced filling errors for width and cross-section, which are current / target - 1 which give deviation from targeted filling and cross-section filling.
• Introduced hooks for choice of how to give them.