Bug 1392: New yang-common/util classes

Bug 1392: New yang-common/util classes

Needed for https://git.opendaylight.org/gerrit/#/c/9178/

OperationFailedException:

   Generalized exception class that contains an RpcError list.

MappingCheckedFuture:

   Futures#addCallback and Futures#transform call Future#get but
   CheckedFuture doesn't override the get methods to translate exceptions
   to the checked type. Thus you don't get the checked exception when using
   those Futures methods. This kind of defeats the purpose of CheckedFuture.

   The new MappingCheckedFuture class overrides the get methods to translate exceptions.

ExceptionMapper:

   Generalized class for use with CheckedFuture to translate exceptions to a
   specified exception type.

Change-Id: Idb4c7e8b5c2cf17795de2f3af4278989ac7bd116
Signed-off-by: tpantelis <tpanteli@brocade.com>
Signed-off-by: Robert Varga <rovarga@cisco.com>