Add DatasetService to read and manage `config.json`.

The DatasetService is intended to load and manage any number of
configured data sources as specified in `config.json`. It also
enforces use of Angular's built-in content caching to improve
loading times of already-accessed datasets.

Change-Id: Ibb161a171d6375bf024bf8c0ab051c3f1a97f760

app/js/services/dataset.js

@@ -0,0 +1,56 @@
+'use strict';
+
+var servicesModule = require('./_index.js');
+
+/**
+ * @ngInject
+ */
+function DatasetService($q, $http) {
+
+  var service = {};
+
+  service.list = function() {
+    return $http({
+      cache: true,
+      url: 'data/config.json',
+      method: 'GET'
+    });
+  };
+
+  service.raw = function(dataset) {
+    return $http({
+      cache: true,
+      url: dataset.raw,
+      method: 'GET'
+    });
+  };
+
+  service.details = function(dataset) {
+    return $http({
+      cache: true,
+      url: dataset.details,
+      method: 'GET'
+    });
+  };
+
+  service.tree = function(dataset) {
+    return $http({
+      cache: true,
+      url: dataset.tree,
+      method: 'GET'
+    });
+  };
+
+  service.dstat = function(dataset) {
+    return $http({
+      cache: true,
+      url: dataset.dstat,
+      method: 'GET'
+    });
+  };
+
+  return service;
+
+}
+
+servicesModule.service('datasetService', DatasetService);