Implementation of New Add Tool

Summary:
This is a second version of the new Add Tool and an update to D584.
The tool should draw a polygon like structure with straight lines between control vertices that are set when the user clicks in the image.
Additionally, when the user keeps the mouse button pressed, the tool behaves like the current add tool and the user can manually draw in the image.
The overall behavior is the same as for the LiveWire tool (double click to start new contour, click anywhere to set control point, double click to close contour,...).
The manual draw function when keeping the mouse button pressed is now also integrated in the LiveWire tool.
Note that when modifying a contour, the manual drawn areas should not be modifiable. You can set control points there but they can not be moved.
All other areas of the contour should be modifiable.

Fixes T28464.

Test Plan: manual

Reviewers: O1 MITK Reviewer Group I, O3 MITK Reviewer Group II, kahl, kislinsk

Reviewed By: O1 MITK Reviewer Group I, O3 MITK Reviewer Group II, kislinsk

Subscribers: s434n, floca, kislinsk, kalali

Maniphest Tasks: T28464

Differential Revision: https://phabricator.mitk.org/D609