Fix finetuning, add a finetuning screen, handle errors during importing model, update metadata format, add model exporting

Fix embedded tokenizer loading, implement new model management methods, implement model info loading, model importing

Popup would leave leftover dead popups forever after screen orientation change

* Use RecyclerView for significantly better performance
* Skin tone selector popup

* Shift + swiping space now lets you select text
* Text editor uses more consistent selection logic instead of sending dpad and relying on apps to implement shift+dpad selection, which many of them don't. Dpad is still used for up/down