Add the actual JSON path where Transaction#info is put.

[dmitry-timofeev]

Overview

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See: #904

Definition of Done

• There are no TODOs left in the code
• Change is covered by automated tests
• The coding guidelines are followed
• Public API has Javadoc
• Method preconditions are checked and documented in the Javadoc of the method
• Changelog is updated if needed (in case of notable or breaking changes)
• The continuous integration build passes

[coveralls]

Coverage remained the same at 86.282% when pulling c48d2bc on dmitry-timofeev:more-clarifications-to-info into 9dc4832 on exonum:master.