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.
test search URLs against the string sniffer
add some additional test URLs containing colons
fix string sniffing bugs for URLs containing colons
`runOnMainQueueSync` => `QSGCDMainSync`, `runOnQueueSync` => `QSGCDQueueSync`

+ Bonus helpers.
Remove introduced deprecation warnings.
Revert "Update English strings files with `stringstool`."

This reverts commit 108beabba416da424cef951e9ed78eb0b8284982.
Merge branch 'master' into stringstool
Rename extract to extract-interface-builder + documentation.
Tell which version was used in the file banner.
add a test with one colon