WebSocket adapters

Moving to 3.0. The Core Spring Framework is adding Async support for Spring 3.2 [1]. Furthermore, they are exploring ways to best support Websockets moving forward [2]

As the Spring Integration team would like to align its Websockets/Async support with the Core Spring as much as possible, we will move this adapter to Spring Integration 3.0. In the mean-time, once INT-1958 is fixed, the Atmosphere based adapters will be moved to the Spring Integration Extensions project.

[1] http://blog.springsource.org/2012/05/06/spring-mvc-3-2-preview-introducing-servlet-3-async-support/
[2] https://jira.springsource.org/browse/SPR-9356
[3] https://github.com/cbeams/bitcoin-rt