#SB-213: Switch to maven-indexer:6.0-SNAPSHOT

- Added mapping for indexers.
- Fixed indentation.
#SB-213: Switch to maven-indexer:6.0-SNAPSHOT

- Removed unused import.
#SB-213: Switch to maven-indexer:6.0-SNAPSHOT

- Fixed the context issue.
- Minor polishing/refactoring.

#SB-216: Implement a Spring container shutdown listener which closes the indexer and scanner

- Implemented (committing on branch SB-213).