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

Thanks @DuBearte.

assets/locales/en.json

@@ -507,6 +507,7 @@
   "cmd.sketch_fit_curves_to_section": "Fit Curves to Mesh Section",
   "cmd.sketch_glyphs": "Constraint Glyphs",
   "cmd.sketch_include_3d": "Include 3D Geometry",
+  "cmd.sketch_infinite": "Infinite Line",
   "cmd.sketch_insert_dxf": "Insert DXF",
   "cmd.sketch_insert_svg": "Insert SVG",
   "cmd.sketch_inspect": "Inspect Sketch",
@@ -1139,6 +1140,7 @@
   "ui.homeView": "Home View",
   "ui.horizontal_vertical": "Horizontal/Vertical",
   "ui.import_ellipsis": "Import…",
+  "ui.infinite": "Infinite",
   "ui.insert": "Insert",
   "ui.inspect": "Inspect",
   "ui.intersect": "Intersect",