A few implementation of single zone environment

[x] The temperature violation penalty coefficient alpha should be tuned for reward return in DRL. Maybe just use the same setting as in MPC.
[ ] DRL performs badly at nights, maybe due to varying temperature bounds at night and days.
[x] Power in DRL environment energy cost should be in kW.
[x] Use external file for price definitions. Refactored to issue #39.
[x] Output PCoo.y for total power for single zone temperature control environment.
[x] Discretize damper position into more levels instead of 10. use branch issue36_improve_environment.

YangyangFu / mpc-drl-tl