Improvements regarding utility functions:
* Use constants to define the max and min utility, which are then applied for normalization, reward clipping, and rendering
* Support two additional utility functions (in addition to log): Linear (ie, just data rate) and step function.
* Configurable via CLI. But: Requires manual adjustment of MIN_UTILITY and MAX_UTILITY
**Full Changelog**: https://github.com/CN-UPB/DeepCoMP/compare/v1.3.0...v1.4.0