Translations:Sketcher project/15/en

For 0.12:
 * 1) constraint parameters (datums) editable in the 3D view DONE [jriegel]
 * 2) synchronization between listwidgetview selection - 3D view selection - DONE [wmayer]
 * 3) avoid overlapping of constraints symbols DONE - [mrlukeparry]
 * 4) make constraints symbols smaller, selectable and avoid overlapping when zooming out DONE - [mrlukeparry]
 * 5) create constraint icons for 3D Inventor view DONE - [mrlukeparry]
 * 6) make datum text size dependant on zoom DONE - [mrlukeparry]
 * 7) make datum text easier to select DONE - [mrlukeparry]
 * 8) Prevent text overlap on Datum Labels DONE - [mrlukeparry]
 * 9) testing the new solver in stand alone mode
 * 10) external constraints (having constraints with references outside the sketch, some edge of the 3D model e.g.) 0.13 [jriegel]
 * 11) auto-constraining DONE [jriegel]
 * 12) auto-constraint for perpendicular DONE - [mrlukeparry]
 * 13) visualize tangency constraints DONE - [mrlukeparry]
 * 14) visualize point to line distance constraints and point to point distance constraints DONE - [logari81]
 * 15) add indexes to the constraints symbols in 3D view in order to distinguish between constraints of the same kind DONE - [mrlukeparry]
 * 16) radius constraint (including visualization) DONE - [logari81]
 * 17) angle constraint (including visualization) DONE - [logari81]
 * 18) implement a fillet tool in the sketcher DONE [mrlukeparry]
 * 19) provide a method of setting fillet radius (Issue #437)
 * 20) implement a trim/extend tool in the sketcher DONE [logari81]
 * 21) implement an extend tool SKIPPED [logari81]
 * 22) trim support on arcs DONE [mrlukeparry]
 * 23) equal lengths constraint (including visualization) DONE - [logari81]
 * 24) constrainess diagnostics - degree of freedom counting DONE - [logari81]
 * 25) symmetry constraint (including visualization) DONE -  [logari81]
 * 26) implement point on object constraint DONE - [mrlukeparry]
 * 27) Make Snap-Grid less 'greedy' DONE [mrlukeparry]
 * 28) Wiki page for the Sketcher Workbench DONE [normandc]