Integrate S3 server (minio)

[oeway]

ImJoy exposes api functions such as api.getFileUrl and api.requestUploadUrl to downloading and uploading files, an alternative approach is to integrate a S3 server with minio. S3 interface is much more standardized than our existing http endpoints api, and provides more benefits such as high scalability.

[oeway]

We will support this in a new imjoy-engine implementation.