Duplicate data packets of class 3 transports are not handled properly

The current stack implementation does not check data packets of class 3 connections for duplicate sequence counts.
So all incoming packets, no matter what seuqnce count they hold, will be processed the same way.

Spec Vol1 3.15, chapter 3-4.4.3:

A 16-bit sequence count value is prepended to all Class 1, 2, and 3 transports.
This value is used to detect delivery of duplicate data packets. Sequence count values are initialized on the
first message production and determined by the transport and trigger type on subsequent
message productions. A resend of old data to maintain the connection shall not cause the
sequence count to change, and a consumer shall ignore data when it is received with a duplicate
sequence count. Consuming applications can use this mechanism to distinguish between new
samples and old samples that were sent to maintain the connection.

In addtion Figure 3-4.5:

If the sequence count is the same as the previous
message, notify the application that a duplicate
message was received and discard data.
Otherwise, notify the application that data has
been consumed.

Necessary adaptions:
If the stack detects duplicate data packets for a class 3 connection it shall retrigger the connection timeout timer
and indicate the application that a duplicate data packet has been received.