Generation of additional test methods should not re-format the already existing

[MichaelPrib]

Currently generating additional test methods causes re-formating of already existing methods. Especially removing of empty lines handicaps readability of the test method.

[ingokuba]

@MichaelPrib This requires a complete overhaul of the whole class building, because neither JavaPoet nor JavaParser support formatting of classes (they always apply the default java formatting).