Adding a test for missing data in the fields specified by FORMAT: it should parse correctly
Added support for non-string/non-character INFO and FORMAT fields that are "." in the VCF file. This means "missing data", so there is now a new , , and all the parsers from  (except the flag parser) will return a  instead of whatever they are actually looking for if they see ".". Also, "." is no longer valid as any sort of  other than .
Adding a test to show how we're supposed to be able to drop trailing fields that aren't GT. At the moment, it doesn't work because the parser missed that aspect of the spec. Also switching the test for missing GT field to actually test for a missing (i.e. trailing-dropped) GT field, instead of verifying that any dropped field in the genotype fails the parser (because that is not what the spec says should happen).