Remove legacy Ray code. (#3121)

* Remove legacy Ray code.

* Fix cmake and simplify monitor.

* Fix linting

* Updates

* Fix

* Implement some methods.

* Remove more plasma manager references.

* Fix

* Linting

* Fix

* Fix

* Make sure class IDs are strings.

* Some path fixes

* Fix

* Path fixes and update arrow

* Fixes.

* linting

* Fixes

* Java fixes

* Some java fixes

* TaskLanguage -> Language

* Minor

* Fix python test and remove unused method signature.

* Fix java tests

* Fix jenkins tests

* Remove commented out code.

python/ray/internal/internal_api.py

@@ -2,7 +2,7 @@ from __future__ import absolute_import
 from __future__ import division
 from __future__ import print_function
 
-import ray.local_scheduler
+import ray.raylet
 import ray.worker
 from ray import profiling
 
@@ -42,7 +42,4 @@ def free(object_ids, local_only=False, worker=None):
         if len(object_ids) == 0:
             return
 
-        if worker.use_raylet:
-            worker.local_scheduler_client.free(object_ids, local_only)
-        else:
-            raise Exception("Free is not supported in legacy backend.")
+        worker.local_scheduler_client.free(object_ids, local_only)