add frontend dir for all pure web frontend dev e.g. polymer

apps/frontend/polymer/README.md

apps/frontend/polymer/bower.json

apps/frontend/polymer/bower_components/iron-ajax/.bower.json

apps/frontend/polymer/bower_components/iron-ajax/.gitignore

apps/frontend/polymer/bower_components/iron-ajax/README.md

apps/frontend/polymer/bower_components/iron-ajax/bower.json

...ontend/polymer/bower_components/iron-ajax/demo/index.html

apps/frontend/polymer/bower_components/iron-ajax/hero.svg

apps/frontend/polymer/bower_components/iron-ajax/index.html

...rontend/polymer/bower_components/iron-ajax/iron-ajax.html

...tend/polymer/bower_components/iron-ajax/iron-request.html

...ontend/polymer/bower_components/iron-ajax/test/index.html

...nd/polymer/bower_components/iron-ajax/test/iron-ajax.html

...polymer/bower_components/iron-ajax/test/iron-request.html

apps/frontend/polymer/bower_components/jquery/.bower.json

.../frontend/polymer/bower_components/jquery/MIT-LICENSE.txt

apps/frontend/polymer/bower_components/jquery/bower.json

apps/frontend/polymer/bower_components/jquery/dist/jquery.js

...ontend/polymer/bower_components/jquery/dist/jquery.min.js

...ntend/polymer/bower_components/jquery/dist/jquery.min.map