[3033] Added DHCP-DDNS configuration paramater parsing to b10-dhcp4

Added configuration paramters to dhcp4 and its spec file to support DHCP-DDNS.
Created new classes D2ClientMgr, D2ClientConfig, and D2CientConfigParser in the
libdhcpsrv.   The new parameters are parsed, validated, and stored  but do
not yet affect behavior.  That will be implemented as a seperate ticket.

src/lib/dhcp_ddns/ncr_io.cc

@@ -18,6 +18,32 @@
 namespace isc {
 namespace dhcp_ddns {
 
+NameChangeProtocol stringToNcrProtocol(const std::string& protocol_str) {
+    if (protocol_str == "UDP") {
+        return NCR_UDP;
+    }
+
+    if (protocol_str == "TCP") {
+        return NCR_TCP;
+    }
+
+    isc_throw(BadValue, "Invalid NameChangeRequest protocol:" << protocol_str);
+}
+
+std::string ncrProtocolToString(NameChangeProtocol protocol) {
+    switch (protocol) {
+    case NCR_UDP:
+        return ("UDP");
+    case NCR_TCP:
+        return ("TCP");
+    default:
+        break;
+    }
+
+    return ("UNKNOWN");
+}
+
+
 //************************** NameChangeListener ***************************
 
 NameChangeListener::NameChangeListener(RequestReceiveHandler&