HSEARCH-1458 Disallow mistaken import statements: create a new CheckStyle AST Check
HSEARCH-1458 Avoid using JGroups helpers instead of JUnit helpers for tests
HSEARCH-1365 Extracting modules

- serialization support (native Java and Avro)
- remote backends (jms and jgroups)
- bumping POM version number to 5.0.0-SNAPSHOT
- centralising surefire config
- addding new dedicated Log interface for JGroups backend
HSEARCH-1365 Refactoring ServiceManager and service contract

- removing ServiceProvider interface and implementations
- adding interfaces Service, Startable and Stoppable into service.spi sub package of engine
- adding new helper class AggregatedClassLoader
- adjusting all code to new service implementation
HSEARCH-1365 Updating distribution bundle and fixing Javadoc generation warnings