aa.formExternalConfiguration extension

In my current project I have the requirement to be able to pull validation specs from
the server, instead of having them hardcoded in the HTML.
To achieve this I've created what I call the 'aa.formExternalConfiguration' extension.
Its basically one directive that wraps form elements and decorates these with validation attributes according
to a JavaScript object that contains the specifications.

I've added a bunch of example usages in the ngdoc comments, there's also unit tests for the directive.

I thought this might be an interesting addition to AngularAgility, please have a look and tell me what you think.

This is the first commit of my code, so there might still be some bugs lurking here and there.