Add/Update the logs in Mac class (#1629)

This commit contains the following changes:

- Updates logs for a failed tx or rx to include info about the
  frame (len, seq number, type, src/dst address, etc.).

- Adds detailed logs about transmitted or received Beacon frames
  (network name, xpanid, protocol id, version, joinability, native
  flag, ...)

- Adds helper method `ToInfoString()` to `Frame` and `BeaconPyalod`
  classes to provide a debug info string representation of the
  object.

include/openthread/types.h

@@ -193,6 +193,7 @@ typedef enum ThreadError
      * Received a duplicated frame.
      */
     kThreadError_Duplicated = 31,
+
     kThreadError_Error = 255,
 } ThreadError;