Redesign communication framework

[abeham]

The communication framework still reflects mostly the ideas when simulation-based optimization and communication was mixed. Since the simulation-based optimization operators became their own project communication should be simplified and focus on its tasks.

It is not necessary to specify the parameters in a ConstrainedItemList, a simple list should do. Also the type is not really necessary, as the parameters are looked up regarding their name only (this implies that in SimpleSerialization it becomes necessary to transmit the type).

Serialization parts into two operators:

1. Aggregate the necessary variables
   
2. Serialize the variables according to some scheme

This should still be contained in a single operator. A superclass could be used that would do the aggregation and prepare the variables for serialization and derived subclasses could do the serialization by implementing an abstract method.

The current setup of a communication step still involves a lot of operators, which could hopefully grouped together. E.g. the communication operator could be parametrized with the serialization and deserialization operators and applies them when necessary (serialization before sending, deserialization after receiving) which simplifies building the graph a little.

[abeham]

worked on this ticket in r704

[swagner]

Milestone 3.2 deleted

[abeham]

moved to #866

[swagner]

Milestone Iteration 4 deleted

[swagner]

Milestone Current deleted