Delay App.start till App.user is loaded

Summary:
App.user needs to be loaded so we can check a users role and add
relevant routes. Delay starting the app till the user is loaded.

Test Plan:
Load the UI
Login, and load the UI again
Go to http://ushv3.dev/settings/forms/1 and reload

Reviewers: aMoniker, shadowhand

Reviewed By: aMoniker, shadowhand

Maniphest Tasks: T683

Differential Revision: https://phabricator.ushahidi.com/D366