- WL#3158: IM: Instance configuration extensions;
  - WL#3159: IM: --bootstrap and --start-default-instance modes

The following new statements have been added:
  - CREATE INSTANCE;
  - DROP INSTANCE;

The behaviour of the following statements have been changed:
  - SET;
  - UNSET;
  - FLUSH INSTANCES;
  - SHOW INSTANCES;
  - SHOW INSTANCE OPTIONS;