Changes unit tests that test integration into actual integration tests

Also moves the antrun task for copying `hydra-core.jar` into the binary folder to the `package` task, to allow running the `test` goal without hydra-parent failing.

Integration tests have the format `*IT.java`, and are run with `maven-failsafe-plugin`.

Some ways to build are now:
`mvn clean test`: Runs unit tests
`mvn clean verify`: Runs unit tests and integration tests
`mvn clean install`: Runs unit tests, integrations tests and installs the artifacts

This will partly resolve #112, but these integration tests should be replaced with mocking unit tests.