Add Zotero.clientName, set to "Zotero" by default

We should eventually replace all hard-coded uses of "Zotero" with this
for use by unofficial versions (which legally can't be called "Zotero").

chrome/content/zotero/xpcom/zotero.js

@@ -213,6 +213,8 @@ Components.utils.import("resource://gre/modules/Services.jsm");
 		
 		this.mainThread = Components.classes["@mozilla.org/thread-manager;1"].getService().mainThread;
 		
+		this.clientName = ZOTERO_CONFIG.CLIENT_NAME;
+		
 		var appInfo = Components.classes["@mozilla.org/xre/app-info;1"]
 			.getService(Components.interfaces.nsIXULAppInfo);
 		this.platformVersion = appInfo.platformVersion;

resource/config.js

@@ -1,5 +1,6 @@
 var ZOTERO_CONFIG = {
 	GUID: 'zotero@chnm.gmu.edu',
+	CLIENT_NAME: 'Zotero',
 	REPOSITORY_URL: 'https://repo.zotero.org/repo/',
 	REPOSITORY_CHECK_INTERVAL: 86400, // 24 hours
 	REPOSITORY_RETRY_INTERVAL: 3600, // 1 hour