Add a few unit tests for Java

[cagdasgerede]

Add a few unit tests for https://github.com/dasher-project/dasher/tree/master/java.

This then can be used later as a model to add more unit tests.

[cagdasgerede]

Merve will work on this.

[cagdasgerede]

Merve,

make sure to check the new Java project structure that uses gradle. Now you can simply focus on writing a few unit tests.

[cagdasgerede]

There is now the underlying mechanical setup with one test class. Next we would need to add many tests to get some test coverage. That will be done in the context of a new issue.