Add method to retrieve given annotation linked to object.

Method useful to retrieve annotation like modulo annotation
added at import time.
Fix class cast exception.
Fix query to load annotations.
Add tests for modulo retrieval.
Add modulo namespace to constant.
Add test to create XML annotation.
Review existing tests.
Add modulo ns to pojos and add test using modulo ns.
Fix documentation.
Add pixels to the list of supported type. Test added too
Improve Java doc.
TEMP workaround for #9813
Image marshal includes zoomLevelScaling
viewport.js $ viewportImage.js pass zoomLevelScaling down to PanoJS
PanoJS handles zoomLevelScaling - default is still 50%
xsd-fu: Move XSLT tests to subdirectory
xsd-fu: Download eggs into egg directory
xsd-fu: Move Genshi into egg directory
xsd-fu: Remove obsolete gen.sh script
xsd-fu: Move python code to python subdirectory