[JavaWorker] Enable java worker support (ray-project#2094)

* Enable java worker support
--------------------------
This commit includes a tailored version of the Java worker implementation from Ant Financial.
The changes for build system, python module, src module and arrow are in other commits, this commit consists of the following modules:
 - java/api: Ray API definition
 - java/common: utilities
 - java/hook: binary rewrite of the Java byte-code for remote execution
 - java/runtime-common: common implementation of the runtime in worker
 - java/runtime-dev: a pure-java mock implementation of the runtime for fast development
 - java/runtime-native: a native implementation of the runtime
 - java/test: various tests

Contributors for this work:
 Guyang Song, Peng Cao, Senlin Zhu,Xiaoying Chu, Yiming Yu, Yujie Liu, Zhenyu Guo

* change the format of java help document from markdown to RST

* update the vesion of Arrow for java worker

* adapt the new version of plasma java client from arrow which use byte[] instead of custom type

* add java worker test to ci

* add the example module for better usage guide

.travis.yml

@@ -20,6 +20,17 @@ matrix:
       osx_image: xcode7
       env: PYTHON=3.5
 
+    - os: linux
+      dist: trusty
+      env:
+        - JDK='Oracle JDK 8'
+        - PYTHON=3.5
+      install:
+        - ./.travis/install-dependencies.sh
+        - export PATH="$HOME/miniconda/bin:$PATH"
+      script:
+      - ./java/test.sh
+
     - os: linux
       dist: trusty
       env: LINT=1

build.sh

@@ -79,7 +79,7 @@ if [[ -z  "$PYTHON_EXECUTABLE" ]]; then
 fi
 echo "Using Python executable $PYTHON_EXECUTABLE."
 
-bash $ROOT_DIR/setup_thirdparty.sh $PYTHON_EXECUTABLE
+bash $ROOT_DIR/setup_thirdparty.sh $PYTHON_EXECUTABLE $LANGUAGE
 
 # Now we build everything.
 if [[ "$LANGUAGE" == "java" ]]; then