Adjust potential energy evaluation in NEQ switching and SMC protocol

[saratk1]

Currently, in our neq module we evaluate the potential energy difference as U_(\lamb_(x_t))(x_t) - U_(\lamb(t-1))(x_t), while in the smc module we calculate U_(\lamb_(t+1))(x_t) - U_(\lamb_(t))(x_t). Maybe we want to adjust this at some point.