Add Neo4j support

Add the support to Neo4j.

Example of command for Neo4j:
```bash
ec2-consistent-snapshot --aws-access-key-id KEY 
                                    --aws-secret-access-key SECRET 
                                    --neo4j  
                                    --neo4j-home=/home/djean/software/ecairn/neo4j 
                                    --neo4j-instance='/home/djean/workspace/conversation/shared/neo4j/development' 
                                    vol1
```