Fix CDH4 compile error due to 'org.mockito' artifacts
SHDP-254 Ease testing of boot packaged apps

- New AbstractBootYarnClusterTests base class
- New spring-yarn-boot-test project due to dependencies
- Allows minicluster testing using same concepts
  familiar with xml/javaconfig testing
Merge remote-tracking branch 'jvalkeal/SHDP-254'