some slug prefill logic (bug 1041722)

Once you start typing into the name field replace all spaces with '-'. Once you deselect you get no more prefill love which also takes care of other locales trying to override the existing slug. It's possible other logic could be added but I couldn't think of any for now.
I have no problem with this approach but it also means once you switch locales the slug will keep updating. You might need to wrap it with the same `isSlugEmpty` check. You're right on the regexp above being weak though it should be closer to django's `slugify`.