2010-03-19
*	Reading order has been simplified: Now there has to be exactly one child for
	the <ReadingOrder> element denoting the nature of the contained objects 
	(<OrderedGroup> or <UnorderedGroup>). <RegionRef> elements are only allowed
	inside a group (and not on <ReadingOrder> level anymore). To convert old files
	to the new format it is always possible to introduce an <UnorderedGroup>
	element as child of <ReadingOrder> and place the existing structure in there.
*	Possible attribute values added in TextTypeSimpleType:
	signature-mark
	catch-word
	marginalia
	footnote
	footnote-continued
	TOC-entry

2010-01-12
*	The number of regions is now 0..unbounded (before it was 1..unbounded)
	This change was necessary to allow instances only containing border or
	print space data
*	In order to reflect this change, the namespace has been updated to
	http://schema.primaresearch.org/PAGE/gts/pagecontent/2010-01-12