Measurement tweaks

Additional fix for 5-10-5 using 10-5-10 (the offset distance was not fixed previously). Closes #195, #196.
If the movement cost is rounded to 0, don't display the label. Closes #196.
Update Polish translation. Closes #199. Thanks @Lioheart!
Fix for movement penalty getting inverted for grid measurement option. Closes #198.
Fix right-click to add waypoints. Closes #197, #192.

Full Changelog: 0.10.8...0.10.9