read model folder then list selectable model

[DorotaLuna]

So that no need to add new models in code, users just download new model and put it into model folder. Also prevent users who doesnt want download model but accidentaly select one.

Registe 2 model folders is used to compatibly with older version

[pythongosssss]

This will mean that you can't automatically download new models as it no longer lists undownloaded ones