Distance measurement tool

A simple tool that measures Euclidian distance on map surface. Works like the one in goggle maps.

Click on button to measure, press ESC to deactivate.

Didn't you always want to know the distance between those two palms?
![screen00251](https://f.cloud.github.com/assets/5911982/1516118/fb70de62-4b0e-11e3-8020-a8f5ebb62241.png)