Add option to indicate if the matched mapping rule is the last one to be processed

To conform with THREESCALE-1344, we should add 1 field to the mapping rules.

• last

This needs to be sent in the response of the API

Backward-compatibility issue:

This is a change in the data model of the mapping rules. If this fields missing it means:

• last = false

In the UI the first iteration will have a toggle per rule because this reflects the actual implementation and expected usage. In a future iteration an 'toggle all' feature might be added if the need arises.