Spring Integration comes with some global properties which can be
configured via `META-INF/spring.integration.properties`. The framework
then provides an `integrationGlobalProperties` bean as an
`org.springframework.integration.context.IntegrationProperties`
instance.

This commit allows users to configure these using regular
`application.properties`. If a `META-INF/spring.integration.properties`
file exists, the values are used as fallback.

See gh-25377