Evaluatable clauses should not be stored in clause_grounding
Evaluatable clauses should not be stored in clause_grounding

This gives weird results like for instance having clause

(NotLink
  (IdenticalLink
    (ConceptNode "A")
    (VariableNode "$Y")
  )
)

associated to ground

(ConceptNopde "C")

in PatternMatchEngine::clause_grounding, given the following pattern
and background knowledge

(AndLink
  (InheritanceLink
    (ConceptNode "A")
    (VariableNode "$X")
  )
  (InheritanceLink
    (VariableNode "$X")
    (VariableNode "$Y")
  )
  (NotLink
    (IdenticalLink
      (ConceptNode "A")
      (VariableNode "$Y")
    )
  )
)

(InheritanceLink
 (ConceptNode "A")
  (ConceptNode "B")
)

(InheritanceLink
  (ConceptNode "A")
  (VariableNode "$X")
)

(InheritanceLink
  (ConceptNode "B")
  (ConceptNode "C")
)

rTreutlein/atomspace,AmeBel/atomspace,yantrabuddhi/atomspace,misgeatgit/atomspace,ArvinPan/atomspace,rTreutlein/atomspace,inflector/atomspace,ArvinPan/atomspace,AmeBel/atomspace,misgeatgit/atomspace,yantrabuddhi/atomspace,rTreutlein/atomspace,misgeatgit/atomspace,AmeBel/atomspace,inflector/atomspace,inflector/atomspace,yantrabuddhi/atomspace,misgeatgit/atomspace,AmeBel/atomspace,inflector/atomspace,ArvinPan/atomspace,inflector/atomspace,yantrabuddhi/atomspace,ArvinPan/atomspace,yantrabuddhi/atomspace,AmeBel/atomspace,rTreutlein/atomspace,rTreutlein/atomspace,misgeatgit/atomspace