Removes h tags from list items

This module displays differently from related modules, like mod_articles_mostread or mod_articles_latest as it sets header tags on the listed items. See attached screenshot: 

![header-levels-in-a-list-of-links](https://f.cloud.github.com/assets/1090182/487652/05ee3450-b962-11e2-8cd2-4940a546a0a6.png)


This fix removes h tags from list items so they appear only on <ul><li> tags, as the other, related modules do. It also removes the header set option from the xml and language files.