Fixed Invalid Character handling in DocumentCache.GetFolder()

InABox.Core/DocumentCache.cs

@@ -363,7 +363,8 @@ namespace InABox.Core
 
         private string GetFolder()
         {
-            return Path.Combine(CoreUtils.GetPath(), DocumentCaches.ServerName ?? "", "_documentcache", Tag);
+            var sanitised = String.Join("_", DocumentCaches.ServerName.Split(System.IO.Path.GetInvalidFileNameChars(), StringSplitOptions.RemoveEmptyEntries) ).TrimEnd('.');
+            return Path.Combine(CoreUtils.GetPath(), sanitised ?? "", "_documentcache", Tag);
         }
 
         private string GetFileName(Guid documentID)