INT-3294 Support Implicit Input Channel with Ann.

JIRA: https://jira.springsource.org/browse/INT-3294

Previously, implicit input channel creation was not
supported for annotated endpoints.

Register a `DirectChannel` if the input channel does
not exist in the context.
INT-3299 Remove Unneeded Dependency From IP

JIRA: https://jira.springsource.org/browse/INT-3299

The IP module incorrectly has s-i-stream as a transitive dependency.

It is only used in a test case.
INT-3404 Clarify Router Attributes

JIRA: https://jira.springsource.org/browse/INT-3304

Add notes to explain the relationship between `resolution-required`
and `default-output-channel`.