Use a module instead of an iframe

http://joomlacode.org/gf/project/joomla/tracker/?action=TrackerItemEdit&tracker_item_id=32230&start=0

This is to fix the issues that hold up the merging of this PR. It is based on the PR #2322 from @elinw. Thank you!! This makes PR #2322 obsolete.

Please be aware that this requires a new round of testing, especially on SQL Azure and Postgres.