Separate python logger module-wise (#2703)

## What do these changes do?
1. Separate the log related code to logger.py from services.py.
2. Allow users to modify logging formatter in `ray start`.

## Related issue number
https://github.com/ray-project/ray/pull/2664

python/ray/services.py

@@ -3,8 +3,8 @@ from __future__ import division
 from __future__ import print_function
 
 import binascii
-import logging
 import json
+import logging
 import os
 import random
 import resource
@@ -28,12 +28,6 @@ import ray.global_scheduler as global_scheduler
 import ray.local_scheduler
 import ray.plasma
 
-logger = logging.getLogger("ray")
-logger.setLevel(logging.INFO)
-ch = logging.StreamHandler(sys.stderr)
-ch.setLevel(logging.INFO)
-logger.addHandler(ch)
-
 PROCESS_TYPE_MONITOR = "monitor"
 PROCESS_TYPE_LOG_MONITOR = "log_monitor"
 PROCESS_TYPE_WORKER = "worker"
@@ -98,6 +92,11 @@ RAYLET_EXECUTABLE = os.path.join(
 ObjectStoreAddress = namedtuple("ObjectStoreAddress",
                                 ["name", "manager_name", "manager_port"])
 
+# Logger for this module. It should be configured at the entry point
+# into the program using Ray. Ray configures it by default automatically
+# using logging.basicConfig in its entry/init points.
+logger = logging.getLogger(__name__)
+
 
 def address(ip_address, port):
     return ip_address + ":" + str(port)