[Umbrella] Native YARN framework layer for services and beyond

(See overview doc at YARN-4692, modifying and copy-pasting some of the relevant pieces and sub-section 3.3.1 to track the specific sub-item.)

(This is a companion to YARN-4793 in our effort to simplify the entire story, but focusing on APIs)

So far, YARN by design has restricted itself to having a very low-­level API that can support any type of application. Frameworks like Apache Hadoop MapReduce, Apache Tez, Apache Spark, Apache REEF, Apache Twill, Apache Helix and others ended up exposing higher level APIs that end­-users can directly leverage to build their applications on top of YARN. On the services side, Apache Slider has done something similar.

With our current attention on making services first­-class and simplified, it's time to take a fresh look at how we can make Apache Hadoop YARN support services well out of the box. Beyond the functionality that I outlined in the previous sections in the doc on how NodeManagers can be enhanced to help services, the biggest missing piece is the framework itself. There is a lot of very important functionality that a services' framework can own together with YARN in executing services end­-to­-end.

In this JIRA I propose we look at having a native Apache Hadoop framework for running services natively on YARN.