Bug 1392: Change ReadTransaction#read to return CheckedFuture

Added a ReadFailedException that is used with the CheckedFuture.
Moved the RpcError list from TransactionCommitFailedException to a new base
OperationFailedException in yangtools and also derived ReadFailedException from
OperationFailedException.

Added a static MAPPER in ReadFailedException class using the new generalized base
ExceptionMapper class in yangtools. Also derived
TransactionCommitFailedExceptionMapper from ExceptionMapper.

Modified uses of Futures#makeChecked in the read Tx and write Tx submit
to use the new MappingCheckedFuture class in yangtools (see
https://git.opendaylight.org/gerrit/#/c/9240/ for details).

Change-Id: I5c4f717f0b8664b7d39c1e6f0366525f04e6634d
Signed-off-by: tpantelis <tpanteli@brocade.com>