Enable `CollectTargetedPcrMetrics` and `CalculateHsMetrics` to target multiple baitsets.
- Both command line programs' `TARGET_INTERVALS` argument accept multiple values.
- `CalculateHsMetrics`'s `BAIT_INTERVALS` accepts multiple values.
Merge pull request #7 from broadinstitute/mm_targeted_metrics_multiple_interval_lists

Enable `CollectTargetedPcrMetrics` and `CalculateHsMetrics` to target multiple baitsets.