Refactor vpp-japi

vlib does not allow concurrent connections, hence make sure the Java API
does not allow the user to instantiate them.

Also hide native methods from direct user invocation behind defensive
methods also detect if a particular connection has been terminated.
Disconnect is hidden befind standard close() method, as specified by
AutoCloseable.

Change-Id: Ib5079200ae4216cad84358a2174a41e90271a30b
Signed-off-by: Robert Varga <nite@hq.sk>
diff --git a/vpp-japi/japi/test/vppApi.java b/vpp-japi/japi/test/vppApi.java
index 96ba4a2..87af329 100644
--- a/vpp-japi/japi/test/vppApi.java
+++ b/vpp-japi/japi/test/vppApi.java
@@ -16,13 +16,13 @@
 import java.net.InetAddress;
 import org.openvpp.vppjapi.*;
 
-public class vppApi extends vppConn {
+public class vppApi {
 
     native int controlPing();
     native void test (byte[] array, byte[] array2);
 
     public static void main (String[] args) throws Exception {
-        vppApi api = new vppApi ();
+        vppConn api = new vppConn ();
         String ipv6 = "db01::feed";
         String ipv4 = "192.168.1.1";
         InetAddress addr6 = InetAddress.getByName(ipv6);