8 - Upload directly to S3 - Non-File API browsers

[rnicholus]

Created from #582.

Some notes:

• allow delete file (via local server)
• allow cancel
• allow custom parameters (via x-amz-meta-paramname request params)
• allow file size validation (server-side) via content-length-range policy document property
• allow edit filename
• allow uploading of Blobs
• allow paste image to upload (where supported)
• get key API method
• keyname option: dynamic, uuid, function that is optionally promissory
• public key (access key) option
• ACL option
• allow CORS support
• I will include an optional POST request sent to the server with specific information when the upload has completed. Integrators can also make their own ajax call in their onComplete callback.
• Status codes will be used to determine upload status.
• Error messages from S3 will be parsed and used to display/reporting
• Only inherited property from request that is relevant is endpoint. The endpoint value must be http://{bucketname}.s3.amazonaws.com. "https" is also a valid protocol.
• A success redirect URL will be required to determine upload status. My guess is that the redirect page be on the same origin as the uploader window. So, if I cannot parse the contents of the iframe due to an access violation, this would indicate that the success URL has not been hit (meaning failure).

signatureEndpoint option (POST):

The endpoint that, when passed a JSON policy document, will return a base-64 encoded signature and a base-64 encoded policy document. These items must be sent along with the request to S3. The response is expected to be a JSON response,with both policy and signature properties. For more information on creating a signature, see the AWS article on HTML POST form upload support (http://aws.amazon.com/articles/1434/ and http://docs.aws.amazon.com/AmazonS3/latest/dev/HTTPPOSTExamples.html).

[rnicholus]

Due to lack of JSON support, I do not plan on natively supporting IE7. However, I may not prohibit use of IE7 with the S3 uploader. Normally, I would disable the upload and possibly include a message indicating that this browser is not supported. For integrators that must support IE7 w/ S3 uploads, you can include Douglas Crockford's json2.js polyfill. This should permit the uploader to work correctly in S3 mode.

In #846, we may add the option to include polyfills like json2.js in the combined file for cases such as this.