#20 Add way to delete presets

Presets (pose/hand/face) can only be saved. Presets can't even be overwritten (which is fine imo).

4c4aae4d1b Adds a button that reads the preset folders again and updates the UI appropriately through the changes made in bfbf8113d6.

This allows for modifications (additions, removals etc.) outside of the game to be reflected in MPS when refreshed.