Fixes #58

o Introduces GraphDatabaseSettings#logical_log_rotation_threshold for
  controlling log size for auto-rotation.
o a logical_log_rotation_threshold=0 value means no auto-rotation.
o These two above will replace the setters on XaLogicalLog and
  XaDataSource, namely #setLogicalLogTargetSize() and #setAutoRotate(),
  but they are just deprecated for now.