Add REST API for invoking workflow.

Currently, there is no way to invoking using REST API.
I've added REST API.

json data example:

{
  "op": "workflow.invoke",
  "params": {
    "workplace": "Nova-000",
    "id": "of-overlay.workflow-nova",
    "data": {
      "mgmtIp": "192.168.10.8",
      "ovsdbPort": 6641,
      "sshAccessInfo": {
        "remoteIp": "192.168.10.8",
        "port": 22,
        "user": "root",
        "password": "iloveyou",
        "keyfile": "~/.ssh/id_rsa"
      },
      "ovsDatapathType": "system",
      "physicalPorts": [
        "nova0_1"
      ],
      "vtepIp": "120.0.0.200/24",
      "annotations": {
        "rackId": 1,
        "rackPosition": 3
      }
    }
  }
}

Change-Id: I2ce3bc5a59ce1cbe91c8c6f83bd1f25e81933ce3
diff --git a/apps/workflow/app/src/main/webapp/WEB-INF/web.xml b/apps/workflow/app/src/main/webapp/WEB-INF/web.xml
new file mode 100644
index 0000000..f148fdd
--- /dev/null
+++ b/apps/workflow/app/src/main/webapp/WEB-INF/web.xml
@@ -0,0 +1,60 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+  ~ Copyright 2019-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.
+  -->
+<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xmlns="http://java.sun.com/xml/ns/javaee"
+         xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
+         xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
+         id="ONOS" version="2.5">
+    <display-name>Workflow REST API</display-name>
+
+    <security-constraint>
+        <web-resource-collection>
+            <web-resource-name>Secured</web-resource-name>
+            <url-pattern>/*</url-pattern>
+        </web-resource-collection>
+        <auth-constraint>
+            <role-name>admin</role-name>
+            <role-name>viewer</role-name>
+        </auth-constraint>
+    </security-constraint>
+
+    <security-role>
+        <role-name>admin</role-name>
+        <role-name>viewer</role-name>
+    </security-role>
+
+    <login-config>
+        <auth-method>BASIC</auth-method>
+        <realm-name>karaf</realm-name>
+    </login-config>
+
+    <servlet>
+        <servlet-name>JAX-RS Service</servlet-name>
+        <servlet-class>org.glassfish.jersey.servlet.ServletContainer</servlet-class>
+        <init-param>
+            <param-name>javax.ws.rs.Application</param-name>
+            <param-value>org.onosproject.workflow.rest.WorkflowWebApplication</param-value>
+        </init-param>
+        <load-on-startup>1</load-on-startup>
+    </servlet>
+
+
+    <servlet-mapping>
+        <servlet-name>JAX-RS Service</servlet-name>
+        <url-pattern>/*</url-pattern>
+    </servlet-mapping>
+</web-app>