support to modify filename before sending file to server

[sucotronic]

With this change, you can alter the names of the files being added. I need this in order to support IOS file upload, because in that environment all the images selected are called the same: https://stackoverflow.com/questions/21135037/html-upload-on-iphone-ios-filename-is-always-same-image-jpg-image-png

You can change the name the name of the files after applying this mod the following way:

add: function (e, data) {
  for(var i=0; i<data.files.length ;i++){
    var randomNumber = Math.floor(Math.random()*1000);
    var seconds = Math.floor(new Date().getTime() / 1000);
    var newName = randomNumber+'_'+seconds+'_'+data.files[i].name;
    data.files[i].Aname = newName;
  }
  ...
}

[blueimp]

Thanks for your contribution, @sucotronic

An option to supply an alternative file name has already been added 4 years ago:
0decc74

However I've added support for the uploadName property for blob and non-multipart uploads.

[sucotronic]

Thank you so much. I've reverted my modifications and replaced the property name with the uploadName one, and everything works fine.

Anyway, I've not been able to find any reference to the uploadName property in the library documentation, so it'll be nice to add some kind of reference for other devs ;)

[blueimp]

Agreed regarding documentation.
Any suggestion what would be the best place to add this?

[sucotronic]

After the code example that follows this text:

One special callback is the add callback, as it provides a submit method for the data argument, that will start the file upload:

I'd just put some example code like this:

add: function (e, data) {
    // Change file names before sending to the server
    for(var i=0; i<data.files.length ;i++){
        var randomNumber = Math.floor(Math.random()*1000);
        var newName = randomNumber+'_'+data.files[i].name;
        data.files[i].uploadName = newName;
    }
	data.submit();
}

[blueimp]

Thanks, I've added a section here:
https://github.com/blueimp/jQuery-File-Upload/wiki/API#how-to-provide-alternative-file-names