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/signature.py

@@ -5,10 +5,15 @@ from __future__ import print_function
 from collections import namedtuple
 import funcsigs
 from funcsigs import Parameter
+import logging
 
-from ray.services import logger
 from ray.utils import is_cython
 
+# 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__)
+
 FunctionSignature = namedtuple("FunctionSignature", [
     "arg_names", "arg_defaults", "arg_is_positionals", "keyword_names",
     "function_name"