Vivado-equivalent implementation of Softmax on Quartus

Created by: bo3z

• Implemented fixed_point_utils.py, emulating some fixed-point and bit-manipulation operations in Python. These are usually done through HLS, but are needed in Python for generating LUTs. For reasoning behind Softmax LUT, see Vivado implemenation, in templates/vivado/nnet_utils/nnet_activation.h .
• Stable and Latency implementation of Softmax. Stable performs well (>98%). Like Vivado, Latency approach needs further work to improve accuracy.
• Expanded PyTest to include Softmax tests on Quartus.