pom.xml: updated thymeleaf and thymeleaf-spring to 2.1.4.RELEASE

@see https://github.com/thymeleaf/thymeleaf/blob/thymeleaf-2.1.4.RELEASE/ChangeLog.txt
@see https://github.com/thymeleaf/thymeleaf-spring/blob/thymeleaf-spring4-2.1.4.RELEASE/thymeleaf-spring4/ChangeLog.txt

No functional changes.