Two new information_schema views are added:
* PERIOD table -- columns TABLE_CATALOG, TABLE_SCHEMA, TABLE_NAME,
  PERIOD_NAME, START_COLUMN_NAME, END_COLUMN_NAME.
* KEY_PERIOD_USAGE -- works similar to KEY_COLUMN_USAGE, but for periods.
  Columns CONSTRAINT_CATALOG, CONSTRAINT_SCHEMA, CONSTRAINT_NAME,
  TABLE_CATALOG, TABLE_SCHEMA, TABLE_NAME, PERIOD_NAME

Two new columns are added to the COLUMNS view:
 IS_SYSTEM_TIME_PERIOD_START, IS_SYSTEM_TIME_PERIOD_END - contain YES/NO.