fix(animations): change trigger binding syntax to function as a property binding []

Animation triggers can now be set via template bindings `[]`

BREAKING CHANGE:

animation trigger expressions within the template that are assigned as
an element attribute (e.g. `@prop`) are deprecated. Please use the
Angular2 property binding syntax (e.g. `[@prop]`) when assigning
properties.

```ts
// this is now deprecated
<div @trigger="expression"></div>

// do this instead
<div [@trigger]="expression"></div>
```

modules/@angular/examples/core/animation/ts/dsl/animation_example.ts

@@ -35,7 +35,7 @@ import {Component, animate, state, style, transition, trigger} from '@angular/co
     <button (click)="expand()">Open</button>
     <button (click)="collapse()">Closed</button>
     <hr />
-    <div class="toggle-container" @openClose="stateExpression">
+    <div class="toggle-container" [@openClose]="stateExpression">
       Look at this box
     </div>
   `