Fix Language Selection (closes #547)

[duchampdev]

Checklist

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Description

This PR is meant to fix issue #547. Using appcompat introduces translations for some strings in languages that are not supported by the app. The result is that the app uses these strings from the systems primary language and falls back to the app's default language (English) for all other strings. Using the resConfigs in build.gradle removes all strings apart from the English and German ones. This way, also setups with multiple languages and German as secondary (or tertiary,...) language are supported (for Android >= 7, as multiple languages are only supported from Android 7 on).

[pr1metine]

You need to push more changes to this PR to reinstantiate CI.

[harambasicluka]

Thanks! :)