Fix the scheme API to remove values as well.
Fix the scheme API to remove values as well.

misgeatgit/atomspace,rTreutlein/atomspace,AmeBel/atomspace,AmeBel/atomspace,rTreutlein/atomspace,AmeBel/atomspace,rTreutlein/atomspace,rTreutlein/atomspace,misgeatgit/atomspace,rTreutlein/atomspace,misgeatgit/atomspace,misgeatgit/atomspace,AmeBel/atomspace,AmeBel/atomspace,misgeatgit/atomspace