[GSoC] QuarkXPress import, Week 3

During this week we continued reverse engineering of QuarkXPress 3-4 format
and had some substantial progress:
- Completed object type identification (shape type, content type).
- Refactored object parsing and improved size identification (QXP does not
store sizes/offsets for object records), which should cover most cases now.
Currently only for QXP 3.3, but it should not be difficult to implement in
QXP 4, it's very similar.
- Finished parsing of paragraph styles, rules, tabs.
- Refactored and improved parsing of document structure, block chains. This
should be the ultimate version of it: we may identify new records and
details, but there probably will not be any major changes in document
parsing.
- Identified some object properties: color shade, line/frame style, gap
color, text inset, vertical alignment, baseline offset, ... Looks like we
identified most of the object properties except some more advanced such as
picture cropping.
- Parsing of QXP 4 object properties (they are mostly the same, sometimes
different order or size).
- Linked text boxes.
- Object groups.
- Some progress with QXP 4 deobfuscation, but there are still major issues.