invalid terms compile without error (and insufficient warning)

[ncatlett]

Terms using the functions pmod() or products() as outer functions compile without error or sufficient semantic warning. These BEL functions should be used within a proteinAbundance() or reaction() function, respectively.

Examples:

pmod(p(HGNC:PSEN1))

-this gets a warning that the expected signature for pmod is missing (mod type, aa, position) - nothing about the missing outer function

products(g(HGNC:IL12B),g(HGNC:CXCL10))

-this gets no warning

I suspect that reactants(), sub(), trunc() and fus() will behave similarly. These terms seem to be handled poorly by the API - see related issue for KAM Navigator.