implementation of transitivity via encoding and indexing some extra
existentials.
better tests
+ test for role hierarchy with multiple super-roles (currently fails)
fixing more issues with handling role hierarchies when
processing/reverting negative propagations and forward links, and also
checking then a propagated conclusion is still relevant for the target
context.
fixed production of backward links from forward links + a better size
bound for the collection of fillers of stored negative propagations
a slightly optimized encoding of transitive roles.
fixing all issues with role hierarchies in the branch where transitivity
is handled without indexing new ICEs.