Facilitate component-style sub views

[oliverfoster]

Subject of the enhancement

In some places in Adapt we inject DOM elements from one extension into another. This practise isn't possible with frameworks like VueJS and React. We need to allow instantiation of registered 'component style' views in Adapt.

External examples

VueJS: https://vuejs.org/v2/guide/components-registration.html React: https://reactjs.org/docs/components-and-props.html#composing-components

Expected outcome

This should allow us to move to a more appropriate style of injection, ready for future frameworks, without changing too much.

Suggested implementation

Handlebars

Pass the Adapt model by id.

{{subview name="menu:progress" id=this._id}}

Create a model from the data specified.

{{subview name="component:completionIndicator" model=this}}

JavaScript

var MenuProgress = Backbone.View.extend({
    initialize: function() {

    }
});
Adapt.subviews.register("menu:progress", MenuProgress);

[Link2Twenty]

When it comes time to pick a framework it may be worth looking here for pros and cons https://custom-elements-everywhere.com/