Integrate/subsume the Aspera/http-gateway-sdk-js

[gegles]

Once we feel it's a good time (the sooner the better in my opinion), we can bring in all the HTTP Gateway SDK functionality here.

We can then try to come up with a cohesive API and iterate on new functionalities

[dabrad26]

This may be slightly hard since the Desktop SDK followed and copied some from the Gateway SDK so name collision would exist.

Would be good to see if we can alter the behavior of Desktop and HTTP Gateway to be used more without the end user seeing anything. Like same calls (drag/drop, start, progress...) all work without any dupe calls or splits by consumer.

@dwosk maybe good to have a working session to see what we can do for this?