Replace put-selector with dojo/dom-* modules

Based on unit test runs, this improves performance up to 20% (specifically
in IE11; IE8 actually seems to benefit less).

Code size difference is negligible once minification and compression
come into play (and using dom-construct can actually still manage to be
smaller, when one considers that the dom-* modules are likely to already be
included in the majority of cases anyway).
Ensure that dgrid.css is explicitly loaded in all test pages

(This is preparation for further work. TODO: skin.html)