Add 401 and 403 error messages for put saver

Show the user a slightly more useful message for the case where
they're not correctly authenticated and try to do a "put" save.

(I'm thinking about TiddlyHost, but it should be generally useful.)

WIP. Not sure what to do with the translations. Is it better to
leave them out entirely? Will it fallback to en-GB automatically? Is
there some other standard way to add a placeholder? Should I try
filling them in with Google Translate?

core/language/en-GB/Misc.multids

@@ -28,13 +28,15 @@ Error/EditConflict: File changed on server
 Error/Filter: Filter error
 Error/FilterSyntax: Syntax error in filter expression
 Error/FilterRunPrefix: Filter Error: Unknown prefix for filter run
+Error/Forbidden: Permission denied
 Error/IsFilterOperator: Filter Error: Unknown operand for the 'is' filter operator
 Error/FormatFilterOperator: Filter Error: Unknown suffix for the 'format' filter operator
 Error/LoadingPluginLibrary: Error loading plugin library
 Error/NetworkErrorAlert: `<h2>''Network Error''</h2>It looks like the connection to the server has been lost. This may indicate a problem with your network connection. Please attempt to restore network connectivity before continuing.<br><br>''Any unsaved changes will be automatically synchronised when connectivity is restored''.`
 Error/RecursiveTransclusion: Recursive transclusion error in transclude widget
 Error/RetrievingSkinny: Error retrieving skinny tiddler list
 Error/SavingToTWEdit: Error saving to TWEdit
+Error/Unauthorized: Authentication required
 Error/WhileSaving: Error while saving
 Error/XMLHttpRequest: XMLHttpRequest error code
 InternalJavaScriptError/Title: Internal JavaScript Error

core/modules/savers/put.js

@@ -90,8 +90,11 @@ PutSaver.prototype.save = function(text,method,callback) {
 				// response is textual: "XMLHttpRequest error code: 412"
 				var status = Number(err.substring(err.indexOf(':') + 2, err.length))
 				if(status === 412) { // edit conflict
-					var message = $tw.language.getString("Error/EditConflict");
-					callback(message);
+					callback($tw.language.getString("Error/EditConflict"));
+				} else if(status === 401) { // authentication required
+					callback($tw.language.getString("Error/Unauthorized"));
+				} else if(status === 403) { // permission denied
+					callback($tw.language.getString("Error/Forbidden"));
 				} else {
 					callback(err); // fail
 				}