Data modeller: Fix code formatting (avoid newline brackets)

Suppose we have a data object "Test". The data modeller generates the following code:

public class Test implements java.io.Serializable
{
...
   public Test()
   {
   }

This is how the outcome should look like:

public class Test implements java.io.Serializable {
...
   public Test() {
   }

That's the way our code style is defined in class/method/etc templates, e.g. https://github.com/droolsjbpm/kie-wb-common/blob/master/kie-wb-common-services/kie-wb-common-data-modeller-core/src/main/resources/org/kie/workbench/common/services/datamodeller/codegen/java_class2.vm and we should follow the convention.