#293 #110 #109 Fix layout of the railroad diagrams

• Removed awt for painting lines and arcs.
• Switched to awt.font.TextLayout for accurate text-size estimates.
• Switched to integer positions and sizes to get rid of rounding issues.
• Rewrote choice layout as it created a set unsolvable constraints.
• Fixed many off-by-one issues in layout
• Added tests to check proper computing of values.

Closes #293 (closed) #110 (closed) #109 (closed)