Oops, fixed some mistakes in the last commit
Fixed crash calling -description of CBLQueryRow with a nil value
Lowered ForestDB cache sizes, fixed an insertion bug, fixed target
Better mapping of CBForest errors to CBL status codes
Optimization: Don't update LiveQuery if view update doesn't change anything

* CBLView tracks the last sequence at which anything changed in the
  index (lastSequenceChangedAt). This may be less than lastSequenceIndexed.
* CBLQueryEnumerator.stale returns NO if the view index is up to date and
  the lastSequenceChangedAt hasn't changed since the query ran.
* CBLLiveQuery doesn't send a notification if the view updates but its
  index doesn't change.