Allow continuous rotation

[Jesper Eklund]

This excellent app would be even more usable if it would be possible to rotate continuously rather than just in 90 degrees increments (or at last in a lot smaller increments, say on the order of single degrees).

Preferably one should be able to choose either of the endpoints or the midpoint of the ruler to rotate around,and then rotate the ruler by moving the mouse (or by entering a specific angle in a textbox that appears when pivot point is chosen, but thats not equally usable for an app that has its greatest advantage in providing a scale to compare against rather than making absolute meassurements).