Split database objects to hardcoded-structure objects and blob-stored data object

[jevgenika]

change profile json_metadata = conducting a transaction account_update_operation. Now json_metadata stored directly at account_object.

• [x] Move json_metadata blob to separate database object
• [x] Adapt account_create_operation
• [x] Adapt account_create_evaluator
• [x] Adapt account_update_operation
• [x] Adapt account_update_evaluator
• [x] Add account_metadata_operation
• [x] Add account_metadata_evaluator
• [x] Add posting authorization to account_metadata_operation
• [x] Adapt database_api
• [x] Add tests
• [x] Update cli_wallet to use account_metadata_operation

[kotbegemot]

json_metadata blob storage requires changes in database.

[bitphage]

The complete description of this is issue is here (point 1): https://golos.io/golosio/@golosio/golos-io-predlozheniya-po-soderzhaniyu-khardforkov-i-softforkov

[zxcat]

591

[afalaleev]

Tested. No bugs found. Move to Done.