The cleanup goes by the comments found in
https://codereview.qt-project.org/#change,65366,patchset=6


It removes code and comments identified as unneeded.
It also further minimizes the impact on code outside the
plugin dir.

Change-Id: I22bfe9654d0fb6e0bb8f0018ecbe326cda804223
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>