Implement in View a declarative event map for DOM events

Inspired by backbone.js

Advantages:

* Event handling definitions and code are defined in the same place, and
  handlers are defined at the root view level resulting in cleaner more
  comprehensible code overall
* Uses event delegation, thus being more efficient that individual manual
  events.

Previous discussion/patch: https://gerrit.wikimedia.org/r/#/c/180834/
Examples of views with this new feature:

* https://gerrit.wikimedia.org/r/#/c/180835/
* https://gerrit.wikimedia.org/r/#/c/180836/
* https://gerrit.wikimedia.org/r/#/c/180837/

Change-Id: I22f2e9e12e28542a5b136bfbf478a47fc657ef3e