INTEXT-96: The Java DSL initial implementation

JIRA: https://jira.springsource.org/browse/INTEXT-96

* `MessageChannels` Builder
* Configuration infrastructure
* `Pollers` Builder
* Initial `IntegrationFlows` Builder
* `EndpointConfigurer` Specs
* EIP-methods `from(MessageSource)`, `from(MessageChannel)`, `transform`, `filter`