[rllib] Add a simple REST policy server and client example (#2232)

* wip

* cls

* re

* wip

* wip

* a3c working

* torch support

* pg works

* lint

* rm v2

* consumer id

* clean up pg

* clean up more

* fix python 2.7

* tf session management

* docs

* dqn wip

* fix compile

* dqn

* apex runs

* up

* impotrs

* ddpg

* quotes

* fix tests

* fix last r

* fix tests

* lint

* pass checkpoint restore

* kwar

* nits

* policy graph

* fix yapf

* com

* class

* pyt

* vectorization

* update

* test cpe

* unit test

* fix ddpg2

* changes

* wip

* args

* faster test

* common

* fix

* add alg option

* batch mode and policy serving

* multi serving test

* todo

* wip

* serving test

* doc async env

* num envs

* comments

* thread

* remove init hook

* update

* policy serve

* spaces

* checkpoint

* no train

* fix ppo

* comments1

* fix

* updates

* add jenkins tests

* fix

* fix pytorch

* fix

* fixes

* fix a3c policy

* fix squeeze

* fix trunc on apex

* fix squeezing for real

* update

* remove horizon test for now

* fix race condition

* update

* com

* updat

* add test

* Update run_multi_node_tests.sh

* use curl

* curl

* kill

* Update run_multi_node_tests.sh

* Update run_multi_node_tests.sh

* fix import

* update

test/jenkins_tests/run_multi_node_tests.sh

@@ -253,7 +253,7 @@ docker run --rm --shm-size=10G --memory=10G $DOCKER_SHA \
     --smoke-test
 
 docker run --rm --shm-size=10G --memory=10G $DOCKER_SHA \
-    python /ray/python/ray/rllib/examples/multiagent_mountaincar.py
+    python /ray/python/ray/rllib/examples/legacy_multiagent/multiagent_mountaincar.py
 
 docker run --rm --shm-size=10G --memory=10G $DOCKER_SHA \
-    python /ray/python/ray/rllib/examples/multiagent_pendulum.py
+    python /ray/python/ray/rllib/examples/legacy_multiagent/multiagent_pendulum.py