The binding system makes several properties available for binding in your templates, depending on the context.
* $this : The binding context (the view-model).
* $parent : Explicitly accesses the outer scope from within a compose or repeat template. You may need this when a property on the current scope masks a property on the outer scope. Chainable- eg $parent.$parent.foo is supported.
* $event : The DOM Event in delegate or trigger bindings.
* $index : In a repeat template, the index of the item in the collection.
* $first : In a repeat template, is true if the item is the first item in the array.
* $last : In a repeat template, is true if the item is the last item in the array.
* $even : In a repeat template, is true if the item has an even numbered index.
* $odd : In a repeat template, is true if the item has an odd numbered index.
