Simplified CBP and new results on resnets and RL

1. Loss of plasticity in a class-incremental continual learning problem using resnet-18
2. Loss of plasticity in RL using PPO
3. Simplified the utility measure in CBP
4. Improved ReadMe

v1.0

Replicates all the Continual ImageNet results in the paper https://arxiv.org/abs/2306.13812.