expose stat for throttling (# tunnels we're currently participating in)

router/java/src/net/i2p/router/TunnelManagerFacade.java

@@ -60,4 +60,7 @@ public interface TunnelManagerFacade extends Service {
      *
      */
     boolean isInUse(Hash peer);
+    
+    /** how many tunnels are we participating in? */
+    public int getParticipatingCount();
 }

router/java/src/net/i2p/router/tunnelmanager/PoolingTunnelManagerFacade.java

@@ -202,6 +202,10 @@ public class PoolingTunnelManagerFacade implements TunnelManagerFacade {
         return false;
     }
     
+    public int getParticipatingCount() {
+        return _pool.getParticipatingTunnelCount();
+    }
+    
     /**
      * Aint she pretty?
      *