basic cdn support
use cdn helper to output css and js links
make edu pages to use cdn assets
use cdn assets for all newsletter pages
bugfix: donot use cdn for favicon
add replace task to update requirejs release timestamp automatically
add config for requirejs to use cdnHost as baseUrl
Merge branch 'master' into cdn

* master:
  better error message when exam rooms assign fails
  bugfix: birthday not saving and displaying properly
  bugfix: search not working for some models
  bugfix: checker url
  remove useless logging
  bugfix: real email,username and uuid checking
  bugfix: exam uuid cannot be reused
edu pages use assets from cdn
revert cdn config for test