[BUILD] Adds URLIndicator along with documentation

Adds URLIndicator to the build, testable adding

`openmct.install(new openmct.plugins.URLIndicatorPlugin({
url: 'http://localhost:8080/',
icon: 'check',
interval: 15000,
label: 'Localhost'
}))`

to the openmct file. Also added Documentation about the plugin.

src/plugins/URLIndicatorPlugin/URLIndicator.js

@@ -0,0 +1,97 @@
+/*****************************************************************************
+ * Open MCT, Copyright (c) 2014-2016, United States Government
+ * as represented by the Administrator of the National Aeronautics and Space
+ * Administration. All rights reserved.
+ *
+ * Open MCT is 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.
+ *
+ * Open MCT includes source code licensed under additional open source
+ * licenses. See the Open Source Licenses file (LICENSES.md) included with
+ * this source code distribution or the Licensing information page available
+ * at runtime from the About dialog for additional information.
+ *****************************************************************************/
+
+define(
+    [],
+    function () {
+
+        // Set of connection states; changing among these states will be
+        // reflected in the indicator's appearance.
+        // CONNECTED: Everything nominal, expect to be able to read/write.
+        // DISCONNECTED: HTTP failed; maybe misconfigured, disconnected.
+        // PENDING: Still trying to connect, and haven't failed yet.
+        var CONNECTED = {
+                glyphClass: "ok"
+            },
+            PENDING = {
+                glyphClass: 'caution'
+            },
+            DISCONNECTED = {
+                glyphClass: "err"
+            };
+        function URLIndicator($http, $interval) {
+            var self = this;
+            this.icon = "icon-" + (this.options.icon ? this.options.icon : "database");
+            this.URLpath = this.options.url;
+            this.label = this.options.label ? this.options.label : this.options.url;
+            this.interval = this.options.interval || 10000;
+            this.state = PENDING;
+
+            function handleError(e) {
+                self.state = DISCONNECTED;
+            }
+            function handleResponse() {
+                self.state = CONNECTED;
+            }
+            function updateIndicator() {
+                $http.get(self.URLpath).then(handleResponse, handleError);
+            }
+            updateIndicator();
+            $interval(updateIndicator, self.interval, 0, false);
+        }
+
+        URLIndicator.prototype.getCssClass = function () {
+            return this.icon;
+        };
+        URLIndicator.prototype.getGlyphClass = function () {
+            return this.state.glyphClass;
+        };
+        URLIndicator.prototype.getText = function () {
+            switch (this.state) {
+                case CONNECTED: {
+                    return this.label + " is connected";
+                }
+                case PENDING: {
+                    return "Checking status of " + this.label + " please stand by...";
+                }
+                case DISCONNECTED: {
+                    return this.label + " is offline";
+                }
+            }
+        };
+        URLIndicator.prototype.getDescription = function () {
+            switch (this.state) {
+                case CONNECTED: {
+                    return this.label + " is online, checking status every " +
+                    this.interval + " milliseconds.";
+                }
+                case PENDING: {
+                    return "Checking status of " + this.label + " please stand by...";
+                }
+                case DISCONNECTED: {
+                    return this.label + " is offline, checking status every " +
+                    this.interval + " milliseconds";
+                }
+            }
+        };
+        return URLIndicator;
+    });