Merge changes from topic "CowSequenceOp"

* changes:
  libsnapshot: Switch merge to CowRevMergeOpItr
  libsnapshot: Add seq op support to inspect_cow
  libsnapshot: Add CowRevMergeOpIter
  libsnapshot: Add IsOrderedOp
  libsnapshot: Cleanup iterators
  libsnapshot: Add Sequence Ops