a bit of cleanup

Author: stephanstapel

ZUGFeRD/IInvoiceDescriptorReader.cs

@@ -84,7 +84,7 @@ protected bool _IsReadableByThisReaderVersion(Stream stream, IList<string> valid
             stream.Position = 0;
             using (StreamReader reader = new StreamReader(stream, Encoding.UTF8, true, 1024, true))
             {
-                string data = reader.ReadToEnd().Replace(" ", "");
+                string data = reader.ReadToEnd().Replace(" ", String.Empty);
                 foreach (string validURI in validURIs)
                 {
                     if (data.IndexOf(String.Format(">{0}<", validURI), StringComparison.OrdinalIgnoreCase) >= 0)

ZUGFeRD/InvoiceDescriptor.cs

@@ -1686,7 +1686,7 @@ public TradeLineItem AddTradeLineCommentItem(string lineID, string comment, stri
         /// <param name="billingPeriodStart">Start of billing period</param>
         /// <param name="billingPeriodEnd">End of billing period</param>
         /// <returns>Returns the instance of the trade line item. You might use this object to add details such as trade allowance charges</returns>
-        [Obsolete("BillingPeriod parameters will be removed in version 19.0. Use SetBillingPeriod() instead.")]
+        [Obsolete("BillingPeriod and DeliveryNote parameters will be removed in version 19.0. Use SetBillingPeriod() instead.")]
         public TradeLineItem AddTradeLineItem(string name,
                                     decimal netUnitPrice,
                                     string description = null,

ZUGFeRD/InvoiceDescriptor23CIIWriter.cs

@@ -623,6 +623,7 @@ public override void Save(InvoiceDescriptor descriptor, Stream stream, ZUGFeRDFo
 
             #region SellerTaxRepresentativeTradeParty
             // BT-63: the tax taxRegistration of the SellerTaxRepresentativeTradeParty
+            // BG-11 (SellerTaxRepresentativeTradeParty)
             _writeOptionalParty(Writer, PartyTypes.SellerTaxRepresentativeTradeParty, this.Descriptor.SellerTaxRepresentative, ALL_PROFILES, null, null, this.Descriptor.SellerTaxRepresentativeTaxRegistration);
             #endregion