Upgrade to Spring Boot 1.0.0 GA

... when it [becomes available](https://github.com/spring-projects/spring-boot/issues?milestone=9&state=open).

- [ ] when doing the upgrade, also eliminate `@EnableTransactionManagement` from `SiteConfig`, as this will once again be implicitly enabled per spring-projects/spring-boot#576.
- [ ] investigate changing mapping setting per comment below