LP#1697954 Hold details API additional fleshing

LP#1697954 Hold details API additional fleshing

* Support new flesh options in hold details retrieval API:

include_current_copy
include_usr
include_cancel_cause
include_requestor

* Teach browser client code to use the new flesh options.  This reduces
  the number of API calls significantly for rendering holds grids.

* Add debug logging to existing local-flesh calls to indicate when/if
  additional API fleshing may be needed.

* Remove TODO comment about batching holds to avoid cstore exhaustion,
  which was fixed with LP#1653001.  However, leave the batching in place
  since it noticeably improves UI responsiveness, at the cost of a few
  extra API calls.

Signed-off-by: Bill Erickson <berickxx@gmail.com>