Updated purpose of the patch.

[PATCH] Change HTML thumbnail generator to kdewebkit

This patch changes the thumbnail generate to use QtWebKit (through kdewebkit) such that it can be used in the leaner mobile builds [1]. Note that this patch was originally proposed to resolve http://bugs.kde.org/show_bug.cgi?id=248478, but that issue has already been addressed. As such, this change is very optional.

[1] http://lists.kde.org/?l=kde-core-devel&m=130813188205168&w=2.

Tested by generating thumbnails on the Qt HTML documentation folder (thousands of html files).