use asset manifest instead of entries in config.assets.precompile

closes #7565

app/assets/config/manifest.js

+//= link contact-list.js
+//= link jquery3.js
+//= link jquery_ujs.js
+//= link main.js
+//= link jsxc.js
+//= link bookmarklet.js
+//= link mobile/bookmarklet.js
+//= link mobile/mobile.js
+//= link templates.js
+//= link error_pages.css
+//= link admin.css
+//= link rtl.css

config/application.rb

@@ -72,22 +72,10 @@ module Diaspora
 
     # Precompile additional assets.
     # (application.js, application.css, and all non-JS/CSS in the app/assets are already added)
-    config.assets.precompile += %w[
-      contact-list.js
-      jquery3.js
-      jquery_ujs.js
-      main.js
-      jsxc.js
-      bookmarklet.js
-      mobile/bookmarklet.js
-      mobile/mobile.js
-      templates.js
-
-      error_pages.css
-      admin.css
-      rtl.css
+    config.assets.precompile = %w[
       color_themes/*/desktop.css
       color_themes/*/mobile.css
+      manifest.js
     ]
 
     # See lib/tasks/assets.rake: non_digest_assets