Implement remote command support.

- Defaut port is 7643 (totally arbitrary)

- Using RemoteCommandDMRG, each network can be enabled or disabled (net1 .. net5, xlx):
    ~ $ RemoteCommandDMRG 7643 disable net2
    M: 2021-03-20 11:48:40.494 Command sent: "disable net2" to port: 7643
    M: 2021-03-20 11:48:40.545 OK

- Using RemoteCommandDMRG, a connection status can be retrieved:
    ~ $ RemoteCommandDMRG 7643 status
    M: 2021-03-20 11:49:13.513 Command sent: "status" to port: 7643
    M: 2021-03-20 11:49:13.563 xlx:conn net1:conn net2:n/a net3:n/a net4:conn net5:n/a

A returned string is expected from the socket connection, this is why I did not reuse the MMDVMHost's RemoteCommand (unless MMDVMHost RemoteControl is modified as well).

The exit value can be used in scripting (also 1 if we didn't get any reply).

Conf.h

@@ -241,6 +241,11 @@ public:
 	bool         getDynamicTGControlEnabled() const;
 	unsigned int getDynamicTGControlPort() const;
 
+	// The Remote Control section
+	bool         getRemoteControlEnabled() const;
+	std::string  getRemoteControlAddress() const;
+	unsigned int getRemoteControlPort() const;
+
 private:
 	std::string  m_file;
 	bool         m_daemon;
@@ -393,6 +398,10 @@ private:
 
 	bool         m_dynamicTGControlEnabled;
 	unsigned int m_dynamicTGControlPort;
+
+	bool         m_remoteControlEnabled;
+	std::string  m_remoteControlAddress;
+	unsigned int m_remoteControlPort;
 };
 
 #endif