Using EventMachine for SCP

[dmillar]

We should look into the possibility of using EventMachine as the architecture for DServer. We will write less code, and this will be faster and more stable.

[dicom]

If it can make our code cleaner and simpler, then I think it is probably a good idea, even though it would add a dependency to Ruby DICOM.

It would need to be applied to DClient too though, not just DServer, as these two classes share the same network code in the Link class.

It would mean a considerable rewrite of these classes. To be honest, I dont feel like undertaking this myself at the moment, but I am definitely open to the idea.