Bug 145290: allow deletion of more than one filter at once; r=IanN, sr=neil

suite/locales/en-US/chrome/mailnews/filter.properties

@@ -5,7 +5,7 @@ mustEnterName=You must give this filter a name.
 mustSelectAction=You must select at least one filter action.
 cannotHaveDuplicateFilterTitle=Duplicate Filter Name
 cannotHaveDuplicateFilterMessage=The filter name you entered already exists. Please enter a different filter name.
-deleteFilterConfirmation=Are you sure you want to delete this filter?
+deleteFilterConfirmation=Are you sure you want to delete the selected filter(s)?
 untitledFilterName=Untitled Filter
 filterListBackUpMsg=Your filters do not work because the msgFilterRules.dat file, which contains your filters, could not be read. A new msgFilterRules.dat file will be created and a backup of the old file, called rulesbackup.dat, will be created in the same directory.
 customHeaderOverflow=You've exceeded the limit of 50 custom headers. Please remove one or more custom headers and try again.