feat(ngAria): New module to make a11y easier

Adds various aria attributes to the built in directives.
This module currently hooks into ng-show/hide, input, textarea
button as a basic level of support for a11y. I am using this as a
base for adding more tags into the mix for form direction flow,
making ng-repeat updates atomic but the tags here are the most
basic ones.

Closes #5486 and #1600
I intended for the radio type to be included in `aria-checked` but there isn't any attribute or class that we can monitor to see if an element is checked. We would have to monitor the ng-models' value and compare that against the value/ng-value attribute to figure out which element is checked. So I skipped over that as something that can be added on later and focusing on the simplest cases first. 

I'd be open to implementing any way you can suggest!