Bugs fix

• The angular dimension changes the coordinates of a point causing a false linear dimension of initial segment.
• Added magnetic points on the sides of a rectangle
  magnetic point in the middle of an arc is resolved.
• Crash when using the function junction involving an arc of circle or ellipse.
• Extension of one side of a rectangle or square erased the rest of the entity.
  Extension side of a polygon caused by the insertion of a point with coordinates of 0, 0