Transaction comments

Transaction comments using utility.batch() to group system.remark() with transfers.

This will not be available in Ğ1 runtime, but we are waiting for nodes/rust/duniter-v2s#235 (closed)

It should be cleaned before merging.

assets/sql/EnumsMigration_down.sql

@@ -3,3 +3,4 @@ DROP TABLE IF EXISTS counter_level;
 DROP TABLE IF EXISTS identity_status;
 DROP TABLE IF EXISTS smith_status;
 DROP TABLE IF EXISTS event_type;
+DROP TABLE IF EXISTS comment_type;