JavaTestGenerator produces XML-Test Java files

**Citrus Version**
2.7.8

**Expected behavior**
The `JavaTestGenerator` generates Java Citrus tests.

**Actual behavior**
The `JavaTestGenerator` generates XML Citrus tests.

**Test case sample**
```java
new JavaTestGenerator()
.withAuthor("Sven")
.withDescription("This is a sample java test")
.withName("SampleIT")
.usePackage("com.consol.citrus.sample")
.withFramework(UnitFramework.TESTNG)
.create();
```

generates

```java
/**
* This is a sample java test
*
* @author Sven
* @since 2019-01-14
*/
public class SampleIT extends AbstractTestNGCitrusTest {
@CitrusXmlTest(
name = "SampleIT"
)
@Test
public void sampleIT(@CitrusResource TestRunner testRunner) {
}
}
```

**Additional information**
This issue is important for #450 to reduce testing efforts.

Start by locating the JavaTestGenerator implementation and the tests covering its create() output. Reproduce the provided TestNG example and compare the generated source with the expected Java Citrus test behavior. Done means JavaTestGenerator emits the intended Java test content rather than an XML-test wrapper, with a regression test covering the sample.

Written by the indexing model from the issue text.