Add all partials (templates) in angular's $templateCache as part of compile-static

Summary:
    There is a grunt task for that. It goes over all html files and generates a javascript file which inserts them all in the $templateCache. Now no separate http requests should be made for them.
    Required actions for debug: run "npm run ngtemplates" to generate the templates file. This is part of compile-static also.
    This also needs to be run on each html file change.
    We should add a grunt file changes watcher as part of the requirements for development. It will trigger tasks (we will need that also if/when we decide to use SASS)

Reviewers: cramer, haoyi

Reviewed By: haoyi

Subscribers: changesbot, vishal

Differential Revision: https://tails.corp.dropbox.com/D77825