MARMOTTA-314: fixed potential ClassCastException
Re-Added hash-util methods that were removed from KiWiIO in b5b336bc2eea1d00662fe8593923e14a144e49b3
(now they are in HashUtils where they belong)
Added ContextAwareSesameConnectionBackend to be used with grap-contrained ldpath programs
(this is a follow-up on MARMOTTA-215)