This consolidates our macOS build code so that .DS_Store generation is the same when running make deploy for macOS when building on Linux and macOS, rather than maintaining two version of code that essentially do the same thing (just slightly differently).
It also removes unused code and any AppleScript usage, automates finding translation files and generally simplifies macdeployqtplus. It also gets rid of the annoying “popping up” behaviour during DMG generation, names the created image Bitcoin-Core.dmg rather than Bitcoin-Qt.dmg.