Using APPRIS tags during transcript selection

APPRIS tags are used in the transcript selection process.
See issue #231 for more info

Misc:
adding gencode19 datasources to testdata
adding a checking that ref AND alt don't both == "-" in infer_variant
wiring tx_mode option for gencode in TestUtils which currently didn't do anything
Is this method duplicated elsewhere?  Generally, "-" and "" are the same.  So I worry that this method will cause issues in the future.