Add download support for MacGap

[steedos]

Shows downloads progress in Finder and the Downloads stack

[jeff-h]

Ooh! Sounds interesting. I'd really like you to add a note into the README.md explaining how to use your new stuff from the JavaScript side. Would you mind adding this?

Alternatively, feel free to put that info in a comment here. We're probably going to stop putting all this kind of info in the README soon anyway, as it's growing too big. I hope to migrate it all to the Wiki soon.

[jeff-h]

Need to remove NSLog.

[steedos]

The current code can go download if browser detect a content type of attachment. But i think if there is a way to use javascript to control download will be better.

Just like PhoneGap:
http://docs.phonegap.com/en/3.2.0/cordova_file_file.md.html#FileTransfer
FileTransfer.download

[steedos]

Code looks like this:
https://github.com/phonegap/phonegap/blob/master/lib/ios/CordovaLib/Classes/CDVFileTransfer.m

[jeff-h]

Thanks for the update. I'll have a play with it over the long weekend.

[jeff-h]

Is there a reason this needs to be mandatory for all use-cases?