Fix some Kotlin formatting issues and make source more Kotlin like

[guenhter]

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Description of the PR

@jimschubert

The generated code had a few formatting issues (like too deep indentation).
Also some things are done a little bit differently (like using when instead if-else-cascade).

(details of the change, additional tests that have been done, reference to the issue for tracking, etc)

[wing328]

@guenhter thanks for the PR.

Shall we use something like https://github.com/shyiko/ktlint to check the Kotlin's code format?

[guenhter]

That's not a bad idea. Could really help to keep the code properly formatted.

[jmini]

Thank you a lot for this contribution.

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Shall we use something like https://github.com/shyiko/ktlint to check the Kotlin's code format?
That's not a bad idea. Could really help to keep the code properly formatted.

Please file an other PR for that or at least an issue in order to keep the idea in the TODO list.