refactor - dangling branches, unmarshalGetResponse(), dead code
ToBigInt(), uint64ToBigInt()
decodeValue() - set Type correctly (gauge32 tests)
more detailed debugging; remove extraneous comments
parseUint() - Counter32, Gauge32
verax testing, doco
ToBigInt() - no pdutype
strings passing; calc_length()
decodeValue() using calc_length - needs more work
test - strings working