Schema alterations in transactional mode

[novoj]

Currently, the schema cannot be properly modified during the catalog data lifecycle - only before the data is inserted. We need to handle situations where there is existing data in the database and we want to later create or drop index on it or rename it, drop the date in bulk and so on. In short - the same thing that DDL is for in relational databases. All changes must be able to be executed in both warm-up and transactional mode - so all changes must be able to be rolled back.

[novoj]

Schema operations should be exeucted asynchronously and return futures.