refactor to more idiomatic RAII

* FairMQTransportFactoryZMQ: move the config invariant
    initialization to ctor
  * FairMQChannel: add new ctor that creates usable channel
  * FairMQSocket*: close sockets in dtor
  * FairMQTransportFactory*: terminate context in dtor
  * FairMQChannel: add Bind/Connect facades (for explicit control, e.g. timing)

fairmq/shmem/FairMQSocketSHM.cxx

@@ -627,4 +627,5 @@ int FairMQSocketSHM::GetConstant(const string& constant)
 
 FairMQSocketSHM::~FairMQSocketSHM()
 {
+    Close();
 }

fairmq/shmem/FairMQTransportFactorySHM.cxx

@@ -228,3 +228,7 @@ FairMQ::Transport FairMQTransportFactorySHM::GetType() const
     return fTransportType;
 }
 
+FairMQTransportFactorySHM::~FairMQTransportFactorySHM()
+{
+    Terminate();
+}

fairmq/shmem/FairMQTransportFactorySHM.h

@@ -45,7 +45,7 @@ class FairMQTransportFactorySHM : public FairMQTransportFactory
 
     void SendHeartbeats();
 
-    ~FairMQTransportFactorySHM() override {};
+    ~FairMQTransportFactorySHM() override;
 
   private:
     static FairMQ::Transport fTransportType;