CpePipeline: Number of cores for multi-threading is fixed

The CpePipeline does not allow to change the number of cores that are used for multi-threading.
At the moment all available cores-1 are used. For using the CpePipeline on system that are used by several users always using all-1 cores is rather greedy.

A way to set the number of cores would be really helpful in shared multi-user environments.