ReificationUtils contains too much logic #490

ReificationUtils has a 'reify' method that holds extensive logic to be used 
when reifying an object, e.g. merging reifiable objects or topics when needed 
or throwing an exception if a reifier is being reused. Code that circumvents 
ReificationUtils by invoking ReifiableIF.setReifier directly can lead to 
unwanted behaviour or even corrupted data.

Consider this code:
TopicMapBuilderIF builder = getSomeBuilder();
AssociationIF a1 = builder.makeAssociation(builder.makeTopic());
AssociationIF a2 = builder.makeAssociation(builder.makeTopic());
TopicIF t1 = builder.makeTopic();
TopicIF t2 = builder.makeTopic();
a1.setReifier(t1);
a2.setReifier(t1); // accidents will happen
a2.setReifier(t2); // correct mistake
t1.remove();

DeletionUtils will check for reification when deleting a topic, but the 
'reified' field of t1 was overwritten to a2, so only the reifier of a2 is 
reset. The result of this is that a1.getReifier() will point to a non-existing 
topic, a proxy of what was once t1.

ReificationUtils nicely throws an error when trying to use a topic for 
reification that already reifies another reifiable object. Precisely that logic 
should be included in all .setReifier implementations to prevent missing or 
even faulty behaviour.