Rename device property to have a common format and some code cleanup.

FairMQDevice: Rename property for socket rate logging to have common format (old name is still available for compatibility).
FairMQ: Avoid using std namespace in class headers (may require adding std namespace to some child devices).
FairMQ: A bit of code cleanup
FairMQConfigurable: Stop with an error if a property assignment failed due to incorrect key.

fairmq/examples/req-rep/FairMQExampleClient.cxx

@@ -18,6 +18,8 @@
 #include "FairMQExampleClient.h"
 #include "FairMQLogger.h"
 
+using namespace std;
+
 FairMQExampleClient::FairMQExampleClient()
     : fText()
 {