Modify behavior on Zotero Standalone launch to account for failure

- Close Zotero pane before database is closed prior to reload, instead
  of waiting until reload is complete
- Show an error message if Zotero Standalone is not accessible when it
  should be

components/zotero-service.js

@@ -120,6 +120,7 @@ const xpcomFilesConnector = [
 ];
 
 Components.utils.import("resource://gre/modules/XPCOMUtils.jsm");
+Components.utils.import("resource://gre/modules/Services.jsm");
 
 var instanceID = (new Date()).getTime();
 var isFirstLoadThisSession = true;
@@ -164,6 +165,7 @@ ZoteroContext.prototype = {
 	 */
 	"switchConnectorMode":function(isConnector) {
 		if(isConnector !== this.isConnector) {
+			Services.obs.notifyObservers(zContext.Zotero, "zotero-before-reload", isConnector ? "connector" : "full");
 			zContext.Zotero.shutdown().then(function() {
 				// create a new zContext
 				makeZoteroContext(isConnector);