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
I just kept them on v18 because I didn't want to change them.  I can flip them to 19 and see if they still pass, which would be good because we could remove the 18 versions.