Removed develop.js.

The develop.js is no longer necessary because the code in it has
been merged into the main code.

An empty extension.js has been added to provide a place for UI
customization.

Ticket #2099

install/ui/develop.js

@@ -1,13 +0,0 @@
-/*jsl:import ipa.js */
-
-if (window.location.protocol == 'file:') {
-    IPA.json_url = "test/data";
-    IPA.use_static_files = true;
-
-    IPA.details_refresh_devel_hook = function(entity_name,command,pkey){
-        if ((entity_name === 'host')||(entity_name === 'permission')){
-            command.name =   entity_name+'_show_'+pkey;
-            command.method = entity_name+'_show';
-        }
-    };
-}