Update register() API to take an object with a builder function instead of expect static data

[Ben Petersen]

• if directive doesn't provide extension-args="{{someData}}" should still work with whatever the user passes (meaning if user opts to just return static data, should be fine)
• update to use the builder function
• test with a multi-tiered data structure in the demo to ensure that this is clean
• ensure directives will re-render when data changes. scope should be 2-way binding.

Examples of how this should generally work:

extensionInputProvider.register('main', {
   name: 'endpoint1',
   builder: function(args) {
      // should return static, promise or undefined
     // promise to allow async
      return $q.when([ 
                        foo.get(), 
                        bar.get() 
                     ])
                     .then(function(fooData, barData) {
                        return [
                             // structured data goes here, is defined by the user
                        ];
     });
   }
});

The user then can return structured data as desired. This should be more or less consistent with what exists now. Example:

[
  {
     type: 'link',
     displayName: 'I can now customize this',
     href: 'customizable via context',
     onClick: function() {
        // instead of href
     },
     show: true // optional simple way to show/hide.  user could also just not create this object...
  }
]

The directive responsible for output also needs to provide the data arguments that will be given to the
builder function to render the content:

<div
  extension-output
  extension-name="main"
  extension-types="text link sanitize select"
  extension-args="{{items}}"></div>

[Ben Petersen]

Updated via 1.1.0