Also done lot of simplification and modernization.

The additional sed removes every line after seeing the first line
starting with a #, just like git will do it later as well.

See: http://article.gmane.org/gmane.comp.documentfoundation.libreoffice.devel/26794

To allow frame keywords at the start of the document, we need to:
- a single setter method for all frame properties
- make the parser state know about its document
- make the frame know about its parser state

It's a no-op when there is no group dimensions anyways.

With this, we can phase out the "DateHelper" class...

And a little code cleanup here and there...