feat(grid): add Clone Row to row context menu (closes #227)

Copy the selected row as a new row with primary key columns set to
null so auto-increment values are generated on save.

src/i18n/locales/en.ts

@@ -275,6 +275,7 @@ export default {
     discard: "Discard",
     dismiss: "Dismiss",
     addRow: "Add Row",
+    cloneRow: "Clone Row",
     deleteRow: "Delete Row",
     restoreRow: "Restore Row",
     statusClean: "Clean",

src/i18n/locales/es.ts

@@ -276,6 +276,7 @@ export default {
     discard: "Descartar",
     dismiss: "Cerrar",
     addRow: "Agregar fila",
+    cloneRow: "Clonar fila",
     deleteRow: "Eliminar fila",
     restoreRow: "Restaurar fila",
     statusClean: "Sin cambios",

src/i18n/locales/zh-CN.ts

@@ -274,6 +274,7 @@ export default {
     discard: "放弃",
     dismiss: "关闭",
     addRow: "新增行",
+    cloneRow: "克隆行",
     deleteRow: "删除行",
     restoreRow: "恢复行",
     statusClean: "未改",