367 re write pj model as fpga friendly

[gallenaxel]

Made a new PJ model which is FPGA friendly (at least the encoder part). From what I understand, nn.Unflatten() and nn.ConvTranspose2d isn't supported by hls4ml, so if you have any ideas @PRAkTIKal24 how to fix this, please let me know.

This PR only makes additions to the model file and adds an if statement to the encoder/decoder separate saving function in data_processing.py, so everything should work as before.