INT-3052 RestTemplate with TypeReference for HTTP

JIRA: https://jira.springsource.org/browse/INT-3052

Add support of `ParameterizedTypeReference` as a result of
`expectedResponseTypeExpression` evaluation for
`RestTemplate.exchange` with `ParameterizedTypeReference` parameter

Now `expectedResponseTypeExpression` can be evaluated to `Class<?>`,
`String` and `ParameterizedTypeReference<?>`
INT-3242 Final Polish for 4.0.0.M2

- Rename EiMessageHeaderAccessor to IntegrationMessageHeaderAccessor
- Remove GenericMessage
- Minor TODOs
- Start a new What's new" chapter in the reference

JIRA: https://jira.springsource.org/browse/INT-3242
INT-3245 Remove SI ChannelInterceptor

Replace with the same class from spring-messaging.

JIRA: https://jira.springsource.org/browse/INT-3245
[artifactory-release] Release version 4.0.0.M2
[artifactory-release] Next development version