Sketch: infinite construction lines (#1359) (#1547)

Thanks @DuBearte.

assets/locales/de.json

@@ -305,6 +305,7 @@
   "cmd.sketch_fit_curves_to_section": "Kurven an Netzquerschnitt anpassen",
   "cmd.sketch_glyphs": "Bedingungssymbole",
   "cmd.sketch_include_3d": "3D-Geometrie einbeziehen",
+  "cmd.sketch_infinite": "Unendliche Linie",
   "cmd.sketch_insert_dxf": "DXF einfügen",
   "cmd.sketch_insert_svg": "SVG einfügen",
   "cmd.sketch_inspect": "Skizze prüfen",
@@ -907,6 +908,7 @@
   "ui.home": "Start",
   "ui.homeView": "Startansicht",
   "ui.horizontal_vertical": "Horizontal/Vertikal",
+  "ui.infinite": "Unendlich",
   "ui.insert": "Einfügen",
   "ui.inspect": "Prüfen",
   "ui.intersect": "Schnitt",