[manual] Fetch Handlebars templates using Ajax

...rather than embedding them into index.html.

This is only acceptable for dev, but the next commit adds an alternative
mechanism for prod.

There isn't actually a manual deployment step here.  However, this commit won't
work on staging / prod without the next one (since we don't serve
zephyr/static/templates in prod).

(imported from commit dce7ddfe89e07afc3a96699bb972fd124335aa05)

tools/jslint/check-all.js

@@ -12,7 +12,7 @@ var globals =
     + ' status_classes'
 
     // setup.js
-    + ' templates csrf_token'
+    + ' csrf_token'
 
     // Modules, defined in their respective files.
     + ' compose rows hotkeys narrow reload notifications_bar search subs'
@@ -25,6 +25,9 @@ var globals =
     // tutorial.js
     + ' tutorial'
 
+    // templates.js
+    + ' templates'
+
     // zephyr.js
     + ' all_msg_list home_msg_list narrowed_msg_list current_msg_list get_updates_params'
     + ' add_messages'