SONAR-4832 Fix loading and registration of mapping document
SONAR-4832 Cleanup a bit experiment leftovers

Introduce elasticsearch-test for ES integration tests
Enhance coverage on SearchIndex
Rename node in SearchNode
Unplug index at startup (will be triggered by call from RegisterRule to
RuleRegistry)
SONAR-4832 Refactor session into a member for better readability of DB operations
SONAR-4832 RE-enable indexation of rules at startup
SONAR-4832 Add query to fetch IDs from search form criteria