Added d3 force graph to GUI2 topology

Change-Id: I6860472efaf51ea27fad74e630e687f0c6abad3d
diff --git a/web/gui2/src/main/webapp/app/view/topology/layer/forcesvg/visuals/hostnodesvg/hostnodesvg.component.ts b/web/gui2/src/main/webapp/app/view/topology/layer/forcesvg/visuals/hostnodesvg/hostnodesvg.component.ts
new file mode 100644
index 0000000..4b1f4ab
--- /dev/null
+++ b/web/gui2/src/main/webapp/app/view/topology/layer/forcesvg/visuals/hostnodesvg/hostnodesvg.component.ts
@@ -0,0 +1,52 @@
+/*
+ * Copyright 2018-present Open Networking Foundation
+ *
+ * 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.
+ */
+import {
+    Component,
+    Input,
+    OnChanges,
+    SimpleChanges
+} from '@angular/core';
+import { Host } from '../../models';
+import {LogService} from 'gui2-fw-lib';
+
+/**
+ * The Host node in the force graph
+ *
+ * Note 1: here the selector is given square brackets [] so that it can be
+ * inserted in SVG element like a directive
+ * Note 2: the selector is exactly the same as the @Input alias to make this
+ * directive trick work
+ */
+@Component({
+    selector: '[onos-hostnodesvg]',
+    templateUrl: './hostnodesvg.component.html',
+    styleUrls: ['./hostnodesvg.component.css']
+})
+export class HostNodeSvgComponent implements OnChanges {
+    @Input() host: Host;
+
+    constructor(
+        protected log: LogService
+    ) {
+    }
+
+    ngOnChanges(changes: SimpleChanges) {
+        if (!this.host.x) {
+            this.host.x = 0;
+            this.host.y = 0;
+        }
+    }
+}