qtprotobufgen: Fix code-style infractions

Some parts of qtprotobufgen generates code that is not exactly Qt-style, and should be updated to follow the rules. This includes generating a class with an empty macro (ends up with double-space between 'class'-keyword and the classname), and inline getters (braces are attached, should be on separate line)

Steps of this task is to look over the generated output of the tests, then fix the generator to generate Qt-style code.