Translations:Release notes 0.21/74/en


 * The toolbar button for Constrain refraction (Snell's law) has been removed. Commit ef62fc3
 * The Dimensional Constraints and Quantity Spin Boxes now support the same math as Expressions (Evaluated in place). Pull Request #7124
 * The toolbar buttons for Select redundant constraints and Select conflicting constraints have been removed. Pull request #7568
 * The toolbar button for Stop operation has been removed. Pull request #7569
 * The 'Edit controls' section in the Sketcher dialog has been made optional. Pull request #7572
 * The toolbar button for Select unconstrained DoF has been removed. Pull request #7603
 * The Sketcher toolbar has been split in two: 'Sketcher-edit-mode' and 'Sketcher' (i.e. 'not edit mode'). The Sketcher toolbars that are only for edit-mode are hidden in non-edit-mode, and those only for non-edit-mode are hidden in edit-mode. The Structure toolbar is also hidden in Sketcher. Pull request #7655
 * Carbon copy if possible now uses constraint names in the expressions it creates instead of an index based reference, making it more reliable. Pull request #7688
 * The Sketcher 'Solver Message' taskbox has been simplified. The auto-remove-redundant checkbox has been moved to the Constraint taskbox setting button menu. The auto-update checkbox has been moved to the menu of the update button. Pull request #8864
 * Split now supports more curves (ellipses, parabolas, hyperbolas and B-splines). Pull request #6971