Enter `stringstool`, which can extract localizable strings from IB files.

Expected usage, `./Tools/stringstool extract --output-directory "Localized/en.lproj" "Nibs/*.xib".
Update English strings files with `stringstool`.
Add pjr TODOs.
Rename a misleading variable.
Create the output directory if it doesn't exist.
Don't add duplicate strings more than once.
Add a banner at the top of the extracted file.
Name match variables.
Allow keys to be ignored.
More correct explanation.
Default the third pane for "Assign Abbreviation" to the matched string.
Remove deprecated build settings.
Make all localized `.strings` files UTF-16.

And tell Xcode about it.
Empty localized file.
Move definition around.
Move definition around.
Fix weird selector.
Unused statement.
Remove `(SEL)` casts, ARC doesn't like them.
Make that alloc-init call more straightforward.