* added experience replay and n-step

* implementing distributional q value

* added distributional q-value

* added overview in qac_dist and d4pg

* derived D4PG from DDPG

* fixed a bug when action shape >1

* benchmark D4PG mujoco + minor fixs

-entry for DDPG mujoco
-entry for D4PG mujoco
-config for D4PG mujoco
-fixed style D4PG code
-unittests for QAC distributional

* formatted code

* minor updates (read description)

-added d4pg seria_entry test
-updated comments in QACDIST
-added d4pg in commander register
-added q_value in d4pg return dict
-added priority update in d4pg entry
-added assertion in QACDIST