Issue #361: Add 'Reverse Engineer Point' tool (dismine/valentina)

New issue 361: Add ‘Reverse Engineer Point’ tool https://bitbucket.org/valentinateam/valentina/issues/361/add-reverse-engineer-point-tool

Susan Spencer:

Add a ‘Reverse Engineer Point’ tool which calculates the distance and angle from a given point to a new point and autofills in the formula. This tool would be helpful in implementing issue #258: Add ‘Tracing Mode’.

This is the reverse of the ‘Point from distance and angle’ tool.

Use case: The user selects the ‘Reverse Point’ tool and clicks on the canvas. The dialog box pops up and the user selects the given point to use to calculate distance and angle. The formula is filled in with distance and angle.