S3Upload: abortUpload() and scrubFilename() need to accept file in addition to filename

[basinilya]

It should be possible to upload files having same name. For instance, you can search for a file in Windows Explorer and then drop the search results to a drop zone.

scrubFilename() is supposed to return unique S3 Key for such files, but it's currently impossible to handle duplicates in it because the file object is not passed to it.

abortUpload() also needs the file parameter so it can be passed to scrubFilename()

And it looks like uploadToS3() always creates a new instance of Evaporate and this makes usage of this.evaporate in abortUpload() unreliable. (unless Evaporate.create() returns a singleton. Does it?)