File opening, drag drop

(I'm not sure when to present an issue to openchemlib-js or to openchemlib. Guidance requested)

This is for both openchemlib and openchemlib-js

Drag-drop is only recognizing a very limited set of string-based flavors, I think, and at least at nmrdb dropping a mol file in creates nonsense.

No files, tests, or entry points are identified. Start by reproducing the problem at nmrdb with a dropped mol file, then inspect drag-and-drop handling in both openchemlib and openchemlib-js; done means the mol file is recognized and parsed correctly rather than producing nonsense.

Written by the indexing model from the issue text.