Merge changes Icea2572d,I2633e472,I207c0c93,I10cee76c,Ifd78e8ce,I890b5fcc,Ia0b01f5d...

* changes:
  DfsBlockCache: Update hits to not include contains()
  Add a listener for changes to a DfsObjDatabase's pack files
  Expose the reverse index size in the DfsPackDescription
  Add a DfsPackFile method to get the number of cached bytes
  Expose the list of pack files in the DfsBlockCache
  Add a DFS repository description and reference it in each pack
  Clarify the docstring of DfsBlockCache.reconfigure()
  DFS: A storage layer for JGit