Tune gait cycle for phase-based

[farzadab]

We need to add an artificial phase variable to the base environments (no imitation) in order to use the phase-based method. Since the gait cycle length is fixed it can be constraining for this method so we need to tune the cycle length using either:

• hyper-parameter tuning
• looking at a learned motion and calculate the optimal cycle length based on that

[farzadab]

The current best controller that I have for Walker2D has a gait cycle of 0.8 so I'm using this for the phase-based gait cycle as well.