more fixes in pybullet_gym envs/data.

implement pybullet.setAdditionalSearchPath

examples/pybullet/gym/pybullet_envs/bullet/cartpole_bullet.py

@@ -2,10 +2,10 @@
 Classic cart-pole system implemented by Rich Sutton et al.
 Copied from https://webdocs.cs.ualberta.ca/~sutton/book/code/pole.c
 """
-import os, inspect
+import os,  inspect
 currentdir = os.path.dirname(os.path.abspath(inspect.getfile(inspect.currentframe())))
-print ("current_dir=" + currentdir)
-os.sys.path.insert(0,currentdir)
+parentdir = os.path.dirname(os.path.dirname(currentdir))
+os.sys.path.insert(0,parentdir)
 
 import logging
 import math