in order to support the read_next_instance/take_next_instance
operations, the instances have to have a a logical order. Whie the
previous implementation did have a logical order for inserted instances
(Since they are added in a linked list), we need to support relative
ordering also for non-inserted instances (acording to DDS Spec), so we
just order them in ascending order.
Generation Counters are always needed (e.g. for the calculation of the
view_state, since they are dependent on the reading of samples of the
last generation). As such, the Generation Counters were "converted" to
mandatory fields.
It was decided to connect the DDS Endpoint directly to the RTPS
Endpoint. The history_cache Entity will be converted to a generic
History Cache acording to the RTPS Specification.
Because of consistency requirements the implementation was changed to a
single process/single port RAM design.
This should fully (blindly) implement the RTPS Reader side of the DDS
Entity.
