infer sub- and super-level involvement

[rmnldwg]

Some LNLs have sublevels. E.g., LNL II is further subdivided into IIa and IIb. In some datasets, only the superlevel (II) is reported, in others only the sublevels. This package needs a function to standardize this.

This means for example, that when LNL IIb is involved, the superlevel II must be reported as involved, too. Conversely, when the superlevel II is reported to be healthy, all sublevels (IIa, IIb) must have been healthy as well.