fix some html problems:

- within paragraphs use span instead of div
- phrasing environments are now started automatically
- you can now nest ul lists
paint a checker board pattern behind layout to facilitat pixel counting
make it possible to change the value of already existing rules
add a font with arabic for future tests
make sure the XML parser replaces &#xxx; with proper unicode
fix an inconsistency in the saveload routines, one used tag-name descr, others used file
Merge branch 'master' of https://github.com/roever/STLL