Automate easy plates with 'W'

Hello,

Most plates are correctly recognized by tesseract, add a shortcut to save directly. This speeds up training process considerably.

By the way, can you tell me why you can select multiple images for each plates? e.g I can press `SPACE -> SPACE -> SPACE` and the first 3 images are selected. Is this a bug? Are we supposed to save chars for multiple "images"?