Replace char type in records

[Task #1865 Replace char type in records](https://bugs.openmw.org/issues/1865) done plus apps/opencs/model/tools/bodypartcheck.cpp minor fix and components/esm/loadnpc.h minor fix
i think it could be more adequate something like "possible values" or "used values" as 0-26 is the range of values assumed by mPart but the whole structure didn't seem to me as an enum