PLT-4457 Added AtMention component to better render at mentions (#6563)

* Moved Utils.searchForTerm into an action

* Added easier importing of index.jsx files

* PLT-4457 Added AtMention component to better render at mentions

* Fixed client unit tests

* Fixed merge conflict

* Fixed merge conflicts

webapp/webpack.config.js

@@ -241,7 +241,8 @@ var config = {
         alias: {
             jquery: 'jquery/dist/jquery',
             superagent: 'node_modules/superagent/lib/client'
-        }
+        },
+        extensions: ['.js', '.jsx']
     },
     performance: {
         hints: 'warning'