Enable test

[Theosakamg]

to @esteve : Apply #2 before...

Added :

• CMAKEList testing (Java only)
• Simple Test

[esteve]

@Theosakamg I've added a new function in rcljava_common (https://github.com/esteve/ros2_java/blob/master/rcljava_common/cmake/Modules/FindJavaExtra.cmake#L24) which takes care of adding JUnit tests to CTest, instead of adding them directly in CMakeLists.txt. This has the advantage that it adds all the dependency JARs to the test runner automatically. Let me know if that works for you, thanks!