Extend script to delete unused rows of Localizable.strings

[radekcieciwa]

I've extended your script with an option to remove unused lines from file and saving it to another file. I want to share it. @nst do you want to add it to this repo, or should i create my own cause it's slightly different direction?

All best!

[nst]

Hello, sorry for the delay, as long as you just add options and don't break the existing ones, I take it :) thank you in advance

[leeyimm]

@radekcieciwa, It would be great if you can share your delete functionality.