Feature: Rotate based on length and direction

[slspencer]

Describe the new feature you would like to see in Seamly
Add a Rotate tool where the user inputs the length, or "chord", to rotate selected objects around a selected center point.

1. The user selects objects
2. The user inputs the length (e.g. chord), direction (clockwise or counterclockwise), and rotation point
3. The user selects an object from the dropdown list. This object will rotate using the given length, the remaining objects will rotate respective to this object.
4. The tool calculates the angle with:

clockwise direction =  -1
counterclockwise direction = 1
rotation angle = (direction) * atanD(distance/(length between the rotation point and the object selected in the dropdown list)

5. The tool rotates the objects by the angle using the current Rotate tool.