Translation fixes

Fixes some minor translation issues.
Unfortunately, no. The translation files are in [LLK/scratchr2_translations](https://github.com/LLK/scratchr2_translations/), which is periodically updated from [translate.scratch.mit.edu](http:/translate.scratch.mit.edu/). But we don't have much to worry about, since the string "Save project" [isn't in the editor.po anyway](http://translate.scratch.mit.edu/pt/editor/editor.po/translate/?search=Save%20project&sfields=source&sfields=target). I've added the two missing strings ("Don't save" and "Save project?") to the app's `strings()` method, but that's all I can do inside this PR.