Language generation and file structure

* Move language files to strings/ subdir to be consistent with
   react-sdk
 * Only copy static list of languages (to avoid including
   languages that are only a few percent translated)
 * Make copy-res script work with watch mode
 * Other general cleanups like only write each language file once,
   rather than n times.

src/i18n/strings/ml.json

@@ -0,0 +1,5 @@
+{
+    "Add an email address above to configure email notifications": "ഇ മെയില്‍ അറിയിപ്പുകൾ ലഭിക്കാന്‍ മുകളില്‍ ഇ-മെയില്‍ വിലാസം നല്‍കൂ",
+    "All messages": "എല്ലാ സന്ദേശങ്ങളും",
+    "All messages (loud)": "എല്ലാ സന്ദേശങ്ങളും (ഉച്ചത്തിൽ)"
+}