Support jsonpath indexes in sharding key

[ligurio]

CRUD started support JSON path in #12. We need to support JSON path in sharding key.
I would split a task for two parts:

• support indexes with JSON path, need to teach code to extract values when index with JSON path.
• support sharding key definition with JSON path.

NOTE: DDL module doesn't support map and array types and JSONpath in sharding key, see
tarantool/ddl#81

NOTE: Support of JSON path updates and indexes was added in PR #150 and PR #158.