Introduce palantir java format

[fornwall]

Introduce https://github.com/palantir/palantir-java-format and enforce it (CI will fail on unformatted code, which can be fixed by ./gradlew spotlessApply).

@dwalluck (as you have done recent changes):

1. What do you think about this?
2. Do you have any pending changes you want to merge first (to avoid merge conflicts)?
   • Otherwise, is it a good time to make a 0.12.0 release?

[dwalluck]

@fornwall Just two more left to go on top of #48 and then I'll retest against my app which actually uses the code and that should be everything. I am sure #48 will need rebasing before that, though.