Adding support for loading partials using mustache notation

It was not possible to use the mustache partial notation (>) in templates.  Example:

```
<h3>{{title}}</h3>

{{#items}}
{{>itemTemplate}}
{{#items}}
```

This update allows partials to be specified in the template binding.  Example:

```
<div data-bind='template: {name: "mainTemplate", partials: ["itemTemplate"]}'></div>
```

The mustache template engine will get the template content using the element ids specified in the partials array.