Live filter does not work on folder contents later batches

[tomgross]

Streps to reproduce:
Create enough content so folder contents batches.
Go to second batch page
Use live filter

Plone 5.0.4

[davilima6]

The filter does work but not correctly: it filters everything out (leaving 0 results) for any provided input.

Besides (should open other issues):

1. When user inputs something and then clicks the Query button, Plone should open the Query popover with its initial querystring criteria already filled with that input.
2. We should fix the glyphicon-search because it's currently misguiding: user is visually led to think that it is needed to press that button after providing input in the text field, which isn't true as the filtering happens after every keystroke. I suggest updating the placeholder from "Filter" to "Filter items" (to make the labelling closer to the main search placeholder) and keeping two buttons: one to reinforce this is a search input widget (maybe inside the input field) and another for the Advanced Query popover using glyphicon-filter (or glyphicon-option-horizontal).
3. The filter should locate items containing the query string instead of only starting with it.