…g names (#1711)

* reducing memory required with merging intervals with first name only
  this works around an issue when using a large interval list that completely covers the genome (like a GVCF) where you would end up storing the entire potentially very large list in memory in order to computer an inordinately long name.
* cleaner and better tests

* Implement VariantBundles.

* Separate SnappyLoader into SnappyLoader and SnappyLoaderInternal
 This allows SnappyLoader to function (and correctly respond that snappy is not available)
 in the case where the Snappy library is completely missing. Previously it identified and
 worked around cases where the native code was missing or incompatible, but the java code was required.

* Snappy is still marked as a dependency in gradle so downstream projects have to actively opt out of it.

Replace toPath().toString() with toUriString() this should prevent the scheme from being cutoff unintentionally in beta VCFDecoder. Refactor optional handling for clarity