Make ongoing ownership transfers in status work.

Accomplished by fixing the mismatch between ownership_handoff &
ownership_transfer atoms. All usages now use
riak_core_handoff:ho_type().  Removed _transfer & _handoff suffixes from
atoms, as they are all a type of handoff.
* Translation functions from hash (integer or binary) to partition ID
  and back. Partition IDs are zero-based up to (but not including) ring
  size.
* For user-facing tools, hash_is_partition_boundary/2 can be used to
  verify whether a hash provided by the user is actually the first
  in a partition.
* EQC and unit tests.
Switch to ordsets to prop_only_boundaries faster. Also allow test to run longer to cover more hash space
Make EQC tests easier to scan
Leverage equals/2 per @seancribbs
Implementation of riak-admin handoff [summary|details] commands. In
addition to riak_core_handoff_status (the main module) the following
changes were made to other modules in support of this functionality.
* Refactored riak_core_vnode_manager:handle_call({repair...}) for readability.
* Refactor riak_core_vnode_manager:determine_handoff_target/4 into a series of function headers
* Create riak_core_vnode_manager:all_handoffs
* Some additional fixes for refactoring of handoff_type/ho_type into
  single cohesive type from 07e32b0