Update of behaviour of Sigma Neuron Dynamic Process in fixed-point representation

[ccaccavella]

This update modifies the behavior of the Sigma Delta process in fixed-point representation, specifically within the PySigmaDeltaModelFixed process model. As this update introduces a breaking change, a new class named PySigmaDeltaModelFixedCorrected has been created instead of modifying the existing class.

Key Improvements
New Class Introduction: PySigmaDeltaModelFixedCorrected is introduced to encapsulate the corrected behavior.
Behavior: The new class alters only the delta dynamics, leaving the sigma and activation dynamics of the neuron model unchanged.
Truncation Error Compensation: The corrected delta dynamic keeps track of the last activation sent and compensates for truncation errors.

Usage Instructions
To utilize the PySigmaDeltaModelFixedCorrected class, you can either:

1. Provide the exception_proc_model_map, or
2. Write a custom RunConfig.