Related to PLANET-1942

Currently we are using an exact name match to determine which is the page that describes a category (in order to do navigation). We were using that exact name matching in split-two column, and we are also using it in the page.php and evergreen.php

We should switch to selecting as links the pages that fullfill the following criteria:
a) Are children of the "Explore" page
b) Are in the same category as the current page/post