0-DB: Finalize tools for database inspection and maintenance

[maxux]

It's time to finalize tools for maintaining 0-db namespaces.
This is a main issue to manage

• Compaction tools #35
• Clean tools code and avoid code copy #44
• Implement everything needed for replication #53

Now, we have the library, we can reuse the library code and not copy/paste code.
We have some working database in production, we can reuse theses index/data to have real-world file to test index-rebuild and data-compaction stuff.

Right now, index-dump and integrity-check are useful and working but can be improved, index-rebuild and compaction are not working at all.

[maxux]

Since 9a1adaa, index-rebuild is fully working (with history support).