First commit for GA4GH common classes and Picard runner

you can keep the version you have ilia (minus datasetId) 
(sorry i missed the range before, github doesn't display it)

the only url that will actually work has no sequence and no range params at all (so just readgroupsets/rgsid). i'll figure out what we might support long term and then we can tweak the parser later on if necessary. 

so hopefully just removing datasetId will be an easy enough change - sorry for slowing you down!