feat(cache): Add a JS interface to CacheRegister

Closes #1181
fix(ng-view): cleanup should not destroy an already destroyed scope

Refer https://github.com/angular/angular.dart/issues/1182
and repro https://github.com/chirayuk/sample/tree/issue_1182_leaving_a_nested_ng_view

NgView's register cleanup handlers this way:

    _leaveSubscription = route.onLeave.listen((_) {
      _leaveSubscription.cancel();
      // …
      _cleanUp();
    });

When there are nested ng-views, upon a route change, the parent NgView
calls it's _cleanUp() first (which destroys it's child scope) and then
the child NgView attempts a cleanup.  However, it's child scope is
already detached due to the parent NgView cleaning up causing an
exception.

Stack trace is:

    'package:angular/core/scope.dart': Failed assertion: line 335 pos 12: 'isAttached' is not true.

    STACKTRACE:
    #0      Scope.destroy (package:angular/core/scope.dart:335:12)
    #1      NgView._cleanUp (package:angular/routing/ng_view.dart:130:24)
    #2      NgView._show.<anonymous closure> (package:angular/routing/ng_view.dart:106:15)
    #3      _rootRunUnary (dart:async/zone.dart:730)
    #4      _ZoneDelegate.runUnary (dart:async/zone.dart:462)
    #5      _onRunUnary.<anonymous closure> (package:angular/core/zone.dart:113:63)
    #6      VmTurnZone._onRunBase (package:angular/core/zone.dart:97:16)
    #7      _onRunUnary (package:angular/core/zone.dart:113:17)
    #8      _ZoneDelegate.runUnary (dart:async/zone.dart:462)
    #9      _CustomizedZone.runUnary (dart:async/zone.dart:667)
    #10     _BaseZone.runUnaryGuarded (dart:async/zone.dart:582)
    #11     _BufferingStreamSubscription._sendData (dart:async/stream_impl.dart:333)
    #12     _BufferingStreamSubscription._add (dart:async/stream_impl.dart:263)
    #13     _SyncBroadcastStreamController._sendData.<anonymous closure> (dart:async/broadcast_stream_controller.dart:344)
    #14     _BroadcastStreamController._forEachListener (dart:async/broadcast_stream_controller.dart:297)
    #15     _SyncBroadcastStreamController._sendData (dart:async/broadcast_stream_controller.dart:343)
    #16     _BroadcastStreamController.add (dart:async/broadcast_stream_controller.dart:227)
    #17     Router._leaveCurrentRouteHelper (package:route_hierarchical/client.dart:654:48)
    #18     Router._leaveCurrentRouteHelper (package:route_hierarchical/client.dart:656:47)
    #19     Router._leaveCurrentRoute (package:route_hierarchical/client.dart:645:41)
    #20     Router._leaveOldRoutes (package:route_hierarchical/client.dart:525:30)
    #21     Router._processNewRoute (package:route_hierarchical/client.dart:497:27)
    #22     Router._route.<anonymous closure> (package:route_hierarchical/client.dart:481:29)
    #23     _rootRunUnary (dart:async/zone.dart:730)
    #24     _ZoneDelegate.runUnary (dart:async/zone.dart:462)
    #25     _onRunUnary.<anonymous closure> (package:angular/core/zone.dart:113:63)
    #26     VmTurnZone._onRunBase (package:angular/core/zone.dart:97:16)
    #27     _onRunUnary (package:angular/core/zone.dart:113:17)
    #28     _ZoneDelegate.runUnary (dart:async/zone.dart:462)
    #29     _CustomizedZone.runUnary (dart:async/zone.dart:667)
    #30     _Future._propagateToListeners.handleValueCallback (dart:async/future_impl.dart:488)
    #31     _Future._propagateToListeners (dart:async/future_impl.dart:571)
    #32     _Future._completeWithValue (dart:async/future_impl.dart:331)
    #33     _Future._asyncComplete.<anonymous closure> (dart:async/future_impl.dart:393)
    #34     _rootRun (dart:async/zone.dart:723)
    #35     _ZoneDelegate.run (dart:async/zone.dart:453)
    #36     _onScheduleMicrotask.<anonymous closure> (package:angular/core/zone.dart:117:43)
    #37     VmTurnZone._finishTurn (package:angular/core/zone.dart:143:34)
    #38     VmTurnZone._onRunBase (package:angular/core/zone.dart:104:43)
    #39     _onRunUnary (package:angular/core/zone.dart:113:17)
    #40     _ZoneDelegate.runUnary (dart:async/zone.dart:462)
    #41     _CustomizedZone.runUnary (dart:async/zone.dart:667)
    #42     _BaseZone.runUnaryGuarded (dart:async/zone.dart:582)
    #43     _BaseZone.bindUnaryCallback.<anonymous closure> (dart:async/zone.dart:608)

Closes #1182
fix(web platform): Do not barf on attribute selectors.

See #1189
fix(examples): do not use shadow DOM

This is in preparation for implementing the Testability API and Protractor
end-to-end tests since chromedriver can't handle shadowDom references.
feat(animate): animationsAllowed property to turn off all animations

This is required for writing end-to-end tests against AngularDart apps
that use animations.  In such tests, you typically want to test the
functionality of the application and not necessarily deal with the
animations.  This allows you to turn off all animations in your
production site under test.

The Animate class has a new property, animationsAllowed, which can be
set to false to disable all animations.  When true (the default),
whether or not animations occur depend on the animation module installed
and the AnimationOptimizer.
feat(testability): implement the testability for ProtractorDart

See https://pub.dartlang.org/packages/protractor
fix(introspection): work around http://dartbug.com/17752
fix(introspection): work around additional bugs when working around dartbug 17752
test(e2e): add end-to-end tests using ProtractorDart

https://pub.dartlang.org/packages/protractor
chore(scripts): fix detection of DART_SDK/DART/DARTIUM

Sets the stage to get rid of obsolete DARTSDK.
chore(pubspec): require newer protractor