Allow dynamic sorting of replicas within an iRODSDataObject #819

Possible changes include:

• add a sort method with a parameter that specifies how the iRODSDataObject's replica array should be sorted.
• deprecate, and expeditiously (in next major release) remove top level attributes such as replica_number that refer to individual replicas
• deprecate and (at leisure) remove other top level attributes such as size and modify_time that might traditionally be expected to be POSIX aspects of a simple "file on disk"; and for the pending minor release (v3.4.0), make these into read-only properties that refer to the corresponding attribute of the data replica located at self.replicas[0]. This shouldn't break existing applications.