Py2/py3 script that can download macOS components direct from Apple

Can also now build Internet Recovery USB installers from Windows using dd and 7zip.

Thanks to:

• FoxletFox for FetchMacOS and outlining the URL setup
• munki for his macadmin-scripts
• timsutton for brigadier
• wolfmannight for manOSDownloader_rc off which BuildmacOSInstallApp.command is based