prod: write all logs to single log file.
pom.xml: Spring Data JPA updated to 1.5.1

@see http://docs.spring.io/spring-data/jpa/docs/1.5.1.RELEASE/changelog.txt

No functional changes.
Fix logging of event when logged user opens up absent page.

Before there was an exception in log file:
InvalidDataAccessApiUsageException: detached entity passed to persist: ru.mystamps.web.entity.User

Fix #152