feat(formController): add $setUntouched to propagate untouched state

Closes #9050
chore(docs): refactor the docs app search for better bootup time

This commit refactors how the search index is built. The docsSearch service
is now defined by a provider, which returns a different implementation of
the service depending upon whether the current browser supports WebWorkers
or now.

* **WebWorker supported**: The index is then built and stored in a new worker.
The service posts and receives messages to and from this worker to make
queries on the search index.

* **WebWorker no supported**: The index is built locally but with a 500ms
delay so that the initial page can render before the browser is blocked as
the index is built.

Also the way that the current app is identified has been modified so we can
slim down the js data files (pages-data.js) to again improve startup time.

Closes #9204
Closes #9203
feat($location): add ability to opt-out of <base/> tag requirement in html5Mode

This feature allows disabling Angular's requirement of using a <base/> tag
when using location in html5Mode, for applications that do not require
using $location in html5Mode in IE9. To accomplish this, the $locationProvider.html5Mode 
method has been changed to accept a definition object which can optionally set a 
requireBase property to false, removing the requirement of a <base> tag being present
when html5Mode is enabled.

BREAKING CHANGE: The $location.html5Mode API has changed to allow enabling html5Mode by
    passing an object (as well as still supporting passing a boolean). Symmetrically, the
    method now returns an object instead of a boolean value.

    To migrate, follow the code example below:

    Before:

    var mode = $locationProvider.html5Mode();

    After:

    var mode = $locationProvider.html5Mode().enabled;

Fixes #8934
feat(input): support dynamic element validation

Interpolates the form and form control attribute name, so that dynamic form controls (such as those
rendered in an ngRepeat) will always have their expected interpolated name.

The control will be present in its parent form controller with the interpolated property name, and
this name can change when the interpolated value changes.

Closes #4791
Closes #1404