Make application compatible for OTP releases

I removed `derp` because it's an optional dependency (I use exlager/lager which also hooks into the error_handler), also it caused issues while a relup phase because it's not an OTP compatible application.

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The addition of `datastructures` to the applications list is needed for [exrm](https://github.com/bitwalker/exrm) (resolving dependencies for release bundling).

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PRs for the dependencies of `reagent` address the same issues.