PrimitiveUtil to NullPreventer and collection null prevention

Add: The NullPreventer utility (former PrimitiveUtil) supports null prevention of collections. The utility is renamed because of that addition.
OS package to Classmod & user consistency fix

Add: All classes located in the .worl.comp.os package use Classmod instead of MoCl.
Fix: The user class throws an IllegalStateException if an instance is added to a group it already is a member in.
Program Logic to Classmod

Add: The program logic (everything in .world.comp.program) uses Classmod instead of MoCl.
Fix some remaining MoCl to Classmod issues

Fix: Making the remaining changes for the MoCl to Classmod migration to be complete.
JAXB serialization using context path

Add: jaxb.index files in every necessary package for making the old class registry available to JAXB through a more modular method.
Add: The registry class supports registering context path entries (packages).
Remove: The registry class no longer supports registering classes.
Add: The main class registers the default context path packages.
Add: The ProfileSerializer uses the new context path system.
Remove formatted XML output for profile serialization

Remove: The profile serializer no longer prints out formatted XML documents. That reduces the space required for storing profiles.
Fix the profile serializer test

Fix: The profile serializer test only checks whether the persistent features are equal to each other. In the past it also checked temporary and not persistent features like functions.
Fix some remaining small issues

Fix: Bulk commit for resolving many small issues like code style.