SQL: create index

Summary

Current MR introduces CREATE INDEX command for all tarantool index types. As a breaking change in modifies _pico_index structure.

• Close #544 (closed), #503 (closed)
• Depends on sbroad!411 (merged), tarantool-module!486 (merged)
• Follow-ups: docs#225 (closed), docs#226 (closed), tarantool-module#191