Merge branch 'mz/packwriter'

Merge branch 'mz/packwriter'

* mz/packwriter:
  PackWriter test suite
  Simplified implementation of pack creation: PackWriter
  New CountingOutputStream class - stream decorator
  Rename confusing objects field in ObjectWalk
  Support for RevSort.BOUNDARY in ObjectWalk
  Refactor getRevSort() calls to hasRevSort()
  Add hasRevSort() in RevWalk for faster sorting strategy checking
  Raw-data operations in ObjectLoaders and PackFile
  Format DeltaOfsPackedObjectLoader class
  Format UnpackedObjectLoader class
  Format PackedObjectLoader class
  CRC32 PackIndex tests
  CRC32 support for PackIndex
  Refactor PackIndexV2 - extract binarySearchLevelTwo()
  Tests for PackReverseIndex
  Reverse pack index implementation: PackReverseIndex
  WindowedFile fragments copying: copyToStream()
  Add openObjectInAllPacks() to Repository, exposing packed objects storage
  Integer versions of copyRawTo() and fromRaw() in ObjectId
  Fix typo in PackIndexV2