Fix simple filter layout

The complex filter is `<div class='col-md-3'>label</div><div class='col-md-9'><div class='col-md-9'><input style='width: 400px'/></div><div>+-</div></div>`.
Simple filters are `<div class='col-md-3'><div class='col-md-9'><input style='width:400px'/></div>`.
Therefore the complex filter has two gutters and the simple filter only one.
Wrap the simple filter's col-md-9 div in a second col-md-9 div to make the layouts match.

This pull request is built on top of mark's request #1847.