INT-3105 Add 'task-executor' to JMS MDCA

Add task-attribute to int-jms:message-driven-channel-adapter.

Polishing

Fix white space; add author tags; use class name in parser.
INT-3030 Add Error Channel to RMI Inbound Gateway
INT-3030 Polishing; Docs, Tests

Add test cases for error channel support.

Dynamically discover available RMI port.

Add What's New and `<important/>` to reference.