Add extra filtering options for stock items (#394)

lib/l10n/app_en.arb

@@ -76,6 +76,9 @@
   "attention": "Attention",
   "@attention": {},
 
+   "available": "Available",
+   "@available": {},
+
   "availableStock": "Available Stock",
   "@availableStock": {},
 
@@ -357,6 +360,12 @@
   "filterComponentDetail": "Show component parts",
   "@filterComponentDetail": {},
 
+  "filterExternal": "External",
+  "@filterExternal": {},
+
+  "filterExternalDetail": "Show stock in external locations",
+  "@filterExternalDetail": {},
+
   "filterInStock": "In Stock",
   "@filterInStock": {},