various small to large modifications for making HFC through class Hfc compatible with HFC-DB and the quintuple-based transaction time approach

class Hfc is able to fully customize HFC, e.g., its namespace, tuple store, rule store, and forward chainer objects

extensions to Hfc, ForwardChainer, Namespace, and TupleStore to be able to interpret Hfc-Db init files

Fix tests for modified default.nt and test utils refactoring



See merge request !2

moved my Proxy implementation to de.dfki.lt.hfc.proxy and made global class Pair a local class of ForwardChainer as it is only used in this class

new TupleStore, RuleStore and ForwardChainer files (subjectPosition, predicatePosition, objectPosition instance fields; new constructors) & extended polarity+transaction time axiomatic tuples and entailment rule files

new version of RdfGraph and UriProxy, allowing to access and overwrite values; gc() method still missing

new axiomatic N-tuple file for triples with polarity and transaction time (polarity = true and transtime = 0)