neo4j: Use the `json` library.

Signed-off-by: Jean-Christophe Beaupré <jcbrinfo@users.noreply.github.com>
json_serialization: Use `to_json` to escape characters.

Signed-off-by: Jean-Christophe Beaupré <jcbrinfo@users.noreply.github.com>
nitdoc: Use `to_json` to escape JSON values.

Signed-off-by: Jean-Christophe Beaupré <jcbrinfo@users.noreply.github.com>
json: Allow to buffer writings.

Signed-off-by: Jean-Christophe Beaupré <jcbrinfo@users.noreply.github.com>
nitdoc: Do not overwrite search results.

Fix the main problem of #882 by avoiding the overwriting of a search
entry when 2 entities has the same name.

TODO: Make the presentation of duplicates less ambiguous.

Signed-off-by: Jean-Christophe Beaupré <jcbrinfo@users.noreply.github.com>