Add export functionality to Sensors page

- Create TableToolbarExport component to be used as a slot
  in TableToolbar
- Allows selected table items to be exported

Signed-off-by: Yoshie Muranaka <yoshiemuranaka@gmail.com>
Change-Id: I929347e046af8a5d5188e4c4fd9fc874e067cce5
diff --git a/src/locales/en-US.json b/src/locales/en-US.json
index 9a34b65..4b80328 100644
--- a/src/locales/en-US.json
+++ b/src/locales/en-US.json
@@ -11,6 +11,7 @@
       "download": "Download",
       "edit": "Edit",
       "enable": "Enable",
+      "export": "Export",
       "filter": "Filter",
       "replace": "Replace",
       "save": "Save",