update semantics; added valid, message, and detail
update semantics; added valid, message, and detail

valid will be JSON true if semantically valid; JSON false otherwise

message will contain statement and term semantics in a more concise
form

detail will contain both valid and invalid term signatures for each
term in the BEL expression

OpenBEL/bel_parser,OpenBEL/bel_parser,OpenBEL/bel_parser