Add messagecode resolver format based on application property
Use enum for MessageCodesResolver format

Fixes gh-670
Add support for custom banner

SpringApplication now picks up a classpath:banner.txt
by default, and user can choose a different one with
banner.location. The encoding is banner.encoding.

Fixes gh-458
Prevent duplicate files from getting onto sources
Update Boot version in gradle samples
Upgrade to Spring Integration 4.0