Exploration.alg: First running version of the Partition Exploration.

* Introduce the following Decoders:
  * PartitionMappingDecoderGraph: Updates a PlatformCommunicationGraph to align to an updated PartitionMapping.
  * PartitionMappingIdentityDecoder: Forwards a PartitionMappingEncoding to the Genotype
  * TaskInstanceResourceAlignmentDecoder: Adjusts the sets of valid target resources for allocations & reallocates invalid entries.
* Add the following Exploration Sub Problems:
  * PartitionMappingProblem: Mapping of Partitions to cores. TaskMappings are now defined as Task --> Partition.
  * PlatformCommGraphProblem: Recalculation of communication paths existing in the platform. Required for Message Routing.
  * Add corresponding operators: vary the number of Partitions and their allocation to cores. Also add NOP Operators where needed (Esp. Crossover).
  * Add Copy operations.
* Restructure the MessageRouter(s) to consider changes of the PlatfromCommunicationGraphs.
* Various Adpations to existing task mappings due to the changed target resources.
* Update the DependencyGraph:
  * Simplify the calculation of dependencies.
  * Correctly consider "Pure" identity decoders, i.e., Decoders that only take one input genotype into account and output the same: They would be neglected otherwise.
* Restructure the Mapping class.
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