This PR adds the async actions to the Java API. User can call these async actions to get the FutureAction and use JobWaiter (for SimpleFutureAction) to retrieve job Id.

Author: lirui <rui.li@intel.com>

Closes #2176 from lirui-intel/SPARK-2636 and squashes the following commits:

ccaafb7 [lirui] SPARK-2636: fix java doc
5536d55 [lirui] SPARK-2636: mark the async API as experimental
e2e01d5 [lirui] SPARK-2636: add mima exclude
0ca320d [lirui] SPARK-2636: fix method name & javadoc
3fa39f7 [lirui] SPARK-2636: refine the patch
af4f5d9 [lirui] SPARK-2636: remove unused imports
843276c [lirui] SPARK-2636: only keep foreachAsync in the java API
fbf5744 [lirui] SPARK-2636: add more async actions for java api
1b25abc [lirui] SPARK-2636: expose some fields in JobWaiter
d09f732 [lirui] SPARK-2636: fix build
eb1ee79 [lirui] SPARK-2636: change some parameters in SimpleFutureAction to member field
6e2b87b [lirui] SPARK-2636: add java API for async actions