Add setting for document type

Only these document types make sense (for now):
10 Angebot
12 Bestellung
20 Rechnung

That note is fine, however it should be added to the settings description in the admin area.

+++ b/commerce_winbiz.moduleundefined
@@ -230,7 +230,7 @@ function commerce_winbiz_export_orders($oid_from, $oid_to) {
-  $data[2] = WINBIZ_DEFAULT_TYPE;

+++ b/commerce_winbiz.pages.incundefined
@@ -171,6 +171,14 @@ function commerce_winbiz_admin_settings_form($form, &$form_state) {
+    '#default_value' => variable_get('commerce_winbiz_document_type', 20),

It seems now the constant is no more used. Search for it and remove it. Or use it below in the settings...

+++ b/commerce_winbiz.pages.incundefined
@@ -171,6 +171,14 @@ function commerce_winbiz_admin_settings_form($form, &$form_state) {
+    '#description' => t('Determines what kind of document type will be used to create the imported document. Note that you have to set the document type in your WinBiz website configuration to "By default" in order to make this work.'),

WinBiz - Plz check how we defined to write it consistently...

+++ b/commerce_winbiz.moduleundefined
@@ -6,7 +6,6 @@
-define('WINBIZ_DEFAULT_TYPE', '20');

Keept the constant and use it for the default when using variable get.

Code looks fine for me. I did not have testet the functionality though.

+++ b/commerce_winbiz.moduleundefined
@@ -503,3 +503,14 @@ function commerce_winbiz_get_payment_method_code($payment_method_id) {
+    WINBIZ_DEFAULT_TYPE => t('Order confirmation'),

No, here you need to use the plain value, not the constant!

Added.