Ellipse PoE convergence improvement:

- Original non-squared Ulrich (Gardener method based) error function simplified by radcan (simplify_radical).
- Much better convergence
(cherry picked from commit a74236d4998d5a338adeb95fefb492414c47bf5b)
Reworked DeepSOIC (radcan simplified), non-squared.
(cherry picked from commit 2c118d4a46d3ecb40ea62202e495c4e5214d795d)
Major bug fix: coordinates of one point of a tangent line not taken into account in the partials.

Thanks DeepSOIC!!
(cherry picked from commit 8c29d40aaffb7f1d11a6e93a3cafd575d6a08b48)
fixup whitespace difference
Sketcher: Ellipse: Fix equality constraint with new solver

Code clean up.
Sketcher: Ellipse implementation: Internal Alignment Constraint

- The element to which internal alignment is applied has to be selected last.
- All other elements are added in the order of priority, taking into account existing elements
- Art by Jim (beautiful icons).
Sketcher: Ellipse: Restore internal geometry sketcher tool

The new sketcher tool restores the internal geometry of an element.

Currently only the ellipse is supported.
- improvement of internal alignment: close coordinates to ellipse
- fix icon in TaskSketcherConstraints: major and minor were swapped
Internal Geometry:

This version sets the lines in the exact position so that the solver does not have extra work, and the ellipse does not move when adding internal geometry.

It has lots of solver convergence problems.
Minor bug fix: Internal Alignment constraint

Do not toggle back to normal construction lines that are to be assigned to internal constraint
Bug fix: Adding sketcher-tools to part-design
ArcOfEllipse implementation

Part::Geometry + Python implementation
Basic implementation of Arc of ellipse
ArcOfEllipse creation method
Missing Art by Jim
Compiles but does not allow the elliptical arc to added

- New Constraint to map elliptical arc range with the endpoints of the arc
- Bug fixes on widget element relating to old specific constraints
Bug fixes in the constraint mapping endpoints of arc and range of arc
Point on arcofellipse && Tangent to arcofellipse
Fix tangency icon position for Arcofellipse
Bug fix: Select elements associated to constraints works now for foci internal alignment constraints