OLMIS-6760 Update service to use Spring Boot 2.x * Update to Spring Boot 2.2.x using Spring Boot Gradle plugin. * Because of Spring Boot, also need to update PowerMock to v2. * Spring Security OAuth2 is reconfigured to specific release (2.2.2). * Update Flyway to 6.x because of various Flyway issues from earlier versions. * Because of RAML issues, RAML tester updated and specific version of RAML parser used. * Spring Data method names have been changed (existsById, findById, deleteById), and methods return Optional, not null. * Call of new PageRequest replaced with PageRequest.of. * Reimplement generation of Jasper reports (PDF, CSV, XLS, HTML). * Add Keep-Alive header to API definition because of integration test errors. * Fix checkstyle issue.