Testability refactoring

So the goal here is to:
 - make UnitTest independent on Hive instance running (and so to get rid of hive_test dependency in maven)
 - separate ["service-level"](http://martinfowler.com/bliki/TestPyramid.html) integrational tests from UnitTests 
 - at service-level tests treat each backend equally, implement tests for: Hive, Spark, Prestodb, etc.

This will lead to clarification of dependencies (object graph) of any Z child because we want to mock them effectively. 

Lets start a discussion here on how we archive this.
On [QTest:104](https://github.com/alexander-bzz/zeppelin/blob/a08dbe7318f2371f0e6b7b63157636dd56405c7f/zeppelin-zengine/src/test/java/com/nflabs/zeppelin/zengine/QTest.java#L104) i suggest possible variants of dependency injection for query class

Need a @Leemoonsoo help here