First commit for GA4GH common classes and Picard runner

* The servicePath defaults to `genomics/v1beta/`
* The rootUrl defaults to `https://www.googleapis.com/`
* If you want to hit a non-google specific service (which the java client allows), then that servicePath most likely won't work, which is why we set it to `/`. Once set to `/`, that means the rootUrl needs to include the entire endpoint and so needs to look something like `https://www.googleapis.com/genomics/v1beta`.
* Once the servicePath is screwed up in that way, things like batch and hitting other non-genomics Google APIs will stop working

So, if this code is specific to the Google Genomics API, then it should be a one liner like:
```
Genomics genomics = GenomicsFactory.builder("genomics_denovo_caller").build()
        .fromClientSecretsFile(new File(cmdLine.clientSecretsFilename));
```
from the [denovo caller](https://github.com/googlegenomics/denovo-variant-caller-java/blob/b3d16b9d64029ade40c7f936f758a8a95fcfd28e/src/main/java/com/google/cloud/genomics/denovo/DenovoRunner.java#L74)

hope that clears it up!