Added Apache Hadoop test case & more

* Added Hadoop test case (HadoopTest.java, TestGpuMapper.java & TestGpuReducer.java)
* Modified Hama test case (HamaTest.java & TestGpuBSP.java)
* Added throws Exception to Kernel
`void gpuMethod() throws Exception;`
* Added Main-Class check to RootbeerCompiler.java
* Fixed SentinalCtor issue in VisitorGen.java
* Fixed DontDfsMethods
`<java.io.PrintStream: void println(java.lang.String str)>` to
`<java.io.PrintStream: void println(java.lang.String)>`