- allow definition of indexed properties in interfaces which are neither entities nor relations
#84 throw CdoException if a setter is defined without corresponding getter
#51 rename CDO to XO (classes, interfaces, descriptors)
#51 removed all occurences of CDO from .java files
#51 renamed maven artifacts
#51 changed README
#51 updated documentation
#51 fixed wrong variable name
#51 minor pom.xml fixes