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).

DMRNetwork.cpp

@@ -40,6 +40,7 @@ m_name(name),
 m_location(location),
 m_debug(debug),
 m_socket(local),
+m_enabled(false),
 m_status(WAITING_CONNECT),
 m_retryTimer(1000U, 10U),
 m_timeoutTimer(1000U, 60U),
@@ -108,6 +109,14 @@ bool CDMRNetwork::open()
 	return true;
 }
 
+void CDMRNetwork::enable(bool enabled)
+{
+        if (!enabled && m_enabled)
+                m_rxData.clear();
+
+        m_enabled = enabled;
+}
+
 bool CDMRNetwork::read(CDMRData& data)
 {
 	if (m_status != RUNNING)
@@ -345,9 +354,11 @@ void CDMRNetwork::clock(unsigned int ms)
 			if (m_debug)
 				CUtils::dump(1U, "Network Received", m_buffer, length);
 
-			unsigned char len = length;
-			m_rxData.addData(&len, 1U);
-			m_rxData.addData(m_buffer, len);
+			if (m_enabled) {
+				unsigned char len = length;
+				m_rxData.addData(&len, 1U);
+				m_rxData.addData(m_buffer, len);
+			}
 		} else if (::memcmp(m_buffer, "MSTNAK",  6U) == 0) {
 			if (m_status == RUNNING) {
 				LogWarning("%s, Login to the master has failed, retrying login ...", m_name.c_str());