[uicfg] uicfg.py moves from web/ to web/views/ (prepares #2406609)
We are about to make uicfg selectable. Registrable / selectable views
and helpers live in web/views. Hence the move.
Backward compat is put in place. However CubicWeb imports of uicfg are
updated to the new location.
<div id="ajaxroot">
<div class="ajaxHtmlHead">
<script src="http://foo.js" type="text/javascript"> </script>
</div>
<h1>Hello</h1>
</div>