Provide formatting guidelines through a formatter configuration

[tsaglam]

We currently have no formatting guidelines, thus the project has inconsistent formatting and code style. Thus, we should provide a formatter configuration file for everyone to use. The exact configuration should be discussed in a PR, but it could be based on the JPlag formatter configuration. We could export one from Eclipse.

[TomWerm]

I would say we should use the jplag config for now and if we notice something we can still change the config later @vitruv-tools/maintainers .