Minor DB updates

A node can support multiple streams. Unfortunately, an address can't so there might be multiple entries of the same address for different streams.
Also, store object types. I think we'll need them later, specially in search for public keys we requested.

domain/src/main/java/ch/dissem/bitmessage/entity/ObjectMessage.java

@@ -68,6 +68,10 @@ public class ObjectMessage implements MessagePayload {
         return expiresTime;
     }
 
+    public long getType() {
+        return objectType;
+    }
+
     public ObjectPayload getPayload() {
         return payload;
     }

domain/src/main/java/ch/dissem/bitmessage/utils/UnixTime.java

@@ -0,0 +1,29 @@
+/*
+ * Copyright 2015 Christian Basler
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package ch.dissem.bitmessage.utils;
+
+/**
+ * Created by chris on 18.04.15.
+ */
+public class UnixTime {
+    /**
+     * Returns the time in second based Unix time ({@link System#currentTimeMillis()}/1000)
+     */
+    public static long now() {
+        return System.currentTimeMillis() / 1000;
+    }
+}