updated bel_term function
updated bel_term function

added handling of namespace values "a" and "SET" - values identical to
reserved keywords and BEL functions must be quoted

OpenBEL/openbel-contributions,OpenBEL/openbel-contributions,nbargnesi/openbel-contributions,nbargnesi/openbel-contributions,nbargnesi/openbel-contributions,nbargnesi/openbel-contributions,OpenBEL/openbel-contributions,OpenBEL/openbel-contributions