databases/neo4j: Fix run-time

• Assign UID and GIT to neo4j (both 369)
• Instruct neo4j to run as neo4j user
• Move config directory to PREFIX/etc/neo4j
• Move certificates base directory to PREFIX/etc/neo4j/certificates
• Move data directory to /var/db/neo4j/data
• Move metrics directory to /var/db/neo4j/metrics
• Move import directory to /var/db/neo4j/import
• Fix rc.d script accordingly

Partially based on information from [1] and [2]

PR: 268526 [1]
PR: 228532 [2]

Sponsored by: resulta.sk