Refactoring frontend to one based on angular.js

This means that backend server doesn't render views dynamically,
and just response frontend's request, including http status code and json payload.
So backend doesn't need to know routes sequence of frontends so that the backend is more simple.
view rendering is done by static files using angular.js in frontend

- Added features
 * single page frontend application :
   - frontend isn't refreshed at all for lifetime
     (refresh is urgly feature for mobile webapp)
   - every routing requests are done by ajax based on angluar's $route service
   - frontend open new window to get access token of supported social networks.
     we can't do ajax social network auth page which has different domains with our social-logins
     This is CORS problem and is why our frontend open new window.
   - Recover response error due to authentication

 * node.js server doesn't redirect route after handling request of its frontends
   - node.js just send result of request as json or error status code
     This makes node.js server not to keep routes for frontend view

 TODO:
 1. changing seesion based authentication and authorization to token based one
 2. applying bootstrap including modal for prgress bar