Change http exchange API to pass HTTP Exchange to inquiry type based method

We pass the `HTTP Exchange` that `inquiry` type based methods can take into account the `HTTP Exchange` that triggered them.

This breaks API, but when discussing with @vpelletier we said that at this stage it's probably OK.

I updated `erp5_payline`, the only usage in this repository.

/cc @gabriel @kazuhiko @aurel @georgios.dagkakis 

/reviewed-on !245

bt5/erp5_payline/SkinTemplateItem/portal_skins/erp5_payline/PaylineTransaction_inquiry.xml

@@ -50,7 +50,7 @@
         </item>
         <item>
             <key> <string>_params</string> </key>
-            <value> <string></string> </value>
+            <value> <string>http_exchange_value</string> </value>
         </item>
         <item>
             <key> <string>id</string> </key>

bt5/erp5_system_event/SkinTemplateItem/portal_skins/erp5_system_event/HTTPExchange_setFollowUpAndInquiry.py

-assert context.getFollowUp() is None, context.getFollowUp()
+"""Call HTTPExchange_getFollowUpFor* to find the document to use as follow up
+of this HTTP Exchange and call inquiry type-based method on this document.
+
+To use HTTP Exchange framework:
+ * you must have created categories in portal_categories/http_exchange_resource
+ * your "entry point" script must create an HTTP Exchange using an HTTP Exchange
+   Resource as resource category and confirm this HTTP Exchange.
+   In this entry point script, you should also set source and destination categories
+   if it helps traceability.
+   In this entry point script, you should set request and/or response properties.
+ * you must create HTTPExchange_getFollowUpFor${HTTP Exchange Resource Codification}
+   configuration script that will be called on the context of the HTTP Exchange and
+   will be responsible for returning the document on which inquiry will be done.
+   This script can create a new document and return it to use as follow up if applicable.
+ * you must create a `inquiry` type based method that will be called on this follow up
+   document, recieving the HTTP Exchange as argument.
+
+"""
+assert context.hasFollowUp(), context.getFollowUp()
 
 http_exchange_resource = context.getPortalObject().portal_categories.http_exchange_resource
 resource = context.getResourceValue()
@@ -15,4 +33,4 @@ while True:
 follow_up = getattr(context, 'HTTPExchange_getFollowUpFor' + codification)()
 if follow_up is not None:
   context.setFollowUpValue(follow_up)
-  follow_up.getTypeBasedMethod('inquiry')()
+  follow_up.getTypeBasedMethod('inquiry')(http_exchange_value=context)