JMS Docbook Polishing

Clarify the use of a `TemporaryQueue` with a `<reply-listener/>`
only applies when no `reply-destination` is provided.
INT-3379 - Allow Placeholders for Enums

JIRA: https://jira.spring.io/browse/INT-3379

Change enumerated attributes to a union with xsd:string
to allow placeholders.

JMS and XML deferred to 4.1 due to the amount of
changes needed to the parsers. See INT-3384.