Add abaplint.json + fix a few issues

[FreHu]

I'm adding this just to have a repo with both abaplint and apack dependencies. The config is (pretty much) the clean config from https://github.com/FreHu/abaplint-clean-code

I set up https://github.com/FreHu/abap-deps-apack anyone can reference so that abaplint doesn't complain about missing if_abapgit_manifest.

[CLAassistant]

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