KERML — Documentation of features in Transfers library model is wrong

The Kernel Standard Library model for Transfers includes the following features, documented in subclauses of 9.2.7.2:

• 9.2.7.2.4 flowTransfers
• 9.2.7.2.5 flowTransfersBefore
• 9.2.7.2.7 messageTransfers
• 9.2.7.2.11 transfers
• 9.2.7.2.12 transfersBefore

In all these cases, the "Element" kind is documented simply as "Feature". However, in the normative Transfers.kerml file, all of these features are actually declared as steps.

Update library model specification

Actually, it makes even more sense for these features to be item flows, since they are all typed by Transfer or a specialization of it. And, if these item flows are declared as abstract, then it is not necessary to actually provide the related features for the connector ends of the item flow.