Refactor explorer config into useKnockoutExplorer hook (#397)

Co-authored-by: Steve Faulkner <[email protected]>

test/testExplorer/testExplorer.html

@@ -6,13 +6,5 @@
     <link rel="shortcut icon" href="images/CosmosDB_rgb_ui_lighttheme.ico" type="image/x-icon" />
   </head>
 
-  <body>
-    <iframe
-      id="explorerMenu"
-      name="explorer"
-      class="iframe"
-      title="explorer"
-      src="explorer.html?v=1.0.1&platform=Portal"
-    ></iframe>
-  </body>
+  <body></body>
 </html>