Issue title: Help needed with loading the Dynamic form on Button Click
 Issue body: Hi,

I am following this dynamic form generation to read my JSON response and load the form exactly the way it is done in your code. On load the screen renders successfully and I can see my form.
Now, one of the tags in the form is a button on click of which I need to modify my json object and then would like my screen to be rendered from this updated json object. 
So just to give an example, 
On load my screen looks like this:
<A>
<B> 《ADD》 // ADD is a button
<C>

On click of ADD button, I would like to update my screen as follows:

<A>
<B>
<B> 《ADD》
<C>

I tried to do this by updating my json object on click of the button, but after the update screen remains as it is because the dynamic-form directive doesn't load again.

I would appreciate if you can please suggest a way to do this.

Thank you,
Ravi

 Comments: 
 Comment 0: I am sorry, my example didn't come properly on screen.
Here is my example:

On load my screen looks like:
A
B 《ADD》
C

On click of ADD button, I would like to update my screen as follows:

A
B
B 《ADD》
C

 Comment 1: This functionality will be supported once issue #6 is resolved.  Until then, dynamically updating the form structure isn't possible.

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