Function dependency tree

[Melkiades]

Input: package
Output: data.frame with exported functions (and maybe all for Depends:, with some characterizations like "internal", "badge_status") and their package dependencies, i.e. where it is used or referred to (e.g. in documentation).

Current working solution leverages itdepends package but works only for R/ source code calls. My original implementation was incomplete but string-based.