Using Stream instead of FileStream to upload assets

[VGrigoriev1991]

The current implementation of SDK does not allow using a Stream instead of a FileStream to upload assets using AssetService.

The AssetService itself does nothing with the FileStream input parameter and passes it to the FileUploader, which expects the basic Stream type as input.

This functionality is very necessary when using SDK in clouds for serverless applications, when there are limits on available disk space. To use the FileStream, you must have the file directly on the disk.

The SDK is also designed in such a way that it is not possible to expand functionality of BynderClient/AssetService or use a FileUploader separately for uploading assets.

I'm suggesting a potential small change that I've already submitted as a pull request - #104.

Thanks in advance for your attention.

[ahongbynder]

@VGrigoriev1991 merged your PR, will setup a release either next week or later.