Add MutualExclusiveProperties registry

Add MutualExclusiveProperties message registry entry
and error message.
As per redfish specification, "RegistryPrefixes" and
"MessageIds" are mutually exclusive. So add check for
same in EventService and return MutualExclusiveProperties
error message.

Tested:
 - Create subscription failed with error(bad request)
   when the request body contain both "RegistryPrefixes"
   and "MessageIds".

Change-Id: I4c14f946977bce2ced8a7f96eb85855117fde9a8
Signed-off-by: AppaRao Puli <apparao.puli@linux.intel.com>