Real interfaces for ES

[marcoscaceres]

It would be nice to be able to to define actual interfaces in ES. This would allow more pluggable interfaces for things like databases, etc.

This might fit into the DataSource API from Sysapps!!!!

[marcoscaceres]

So, the idea is that you can provide your own implementation around a DataSource object. So you can then put an async JSON backend, or a in memory backend, etc. on it.