SciDAVis - Improvements SVN-temp

should be exposed. This does mean that Table has to be careful about not
triggering calls into the AbstractAspect API within its undo commands, but
it (hopefully) makes the undo system more robust.
- Removed #includes <QXmlStreamReader> and <QXmlStreamWriter> from
AbstractAspect.h, since it will be included quite often (directly or
indirectly), not always in conjunction with XML handling.