Context rules in PLN Unit test Vol. 2

@cosmoharrigan, this pull request is a continuation of https://github.com/opencog/opencog/pull/887. All context rules work now. ```InductionRule_InheritanceLink``` works now as well. The swapping of the ConceptNodes in that particular case was due to a discrepancy between the order of the inputs in the ListLink and the order of the inputs expected by the rule. Otherwise the error arose due to what I specified in the last pull request.