Use more wrappers in API

[limemloh]

Purpose

Introduce type wrappers and update API to use them instead of primitives.

Changes

Several types have been replaced with a module containing the type itself together with functions for constructing and
converting the type:

• AccountAddress
• ContractAddresss
• CredentialRegistrationId
• Duration
• Timestamp
• Energy

The API now uses dedicated types instead of language primitives for:

• Uses AccountAddress instead of a string with base58 encoding.
• Uses BlockHash instead of a string with hex encoding.
• Uses TranactionHash instead of a string with hex encoding.
• Uses Energy instead of a bigint.
• Uses ReceiveName instead of a string.
• Uses InitName instead of a string.
• Uses ContractName instead of a string.
• Uses EntrypointName instead of a string.
• Uses Parameter instead of a string with hex encoding.
• Uses SequenceNumber (formerly called nonce) instead of a bigint.
• Uses Timestamp instead of a bigint.
• Uses Duration instead of a bigint.

Checklist

• My code follows the style of this project.
• The code compiles without warnings.
• I have performed a self-review of the changes.
• I have documented my code, in particular the intent of the
  hard-to-understand areas.
• (If necessary) I have updated the CHANGELOG.

[soerenbf]

Here's what I found:

Also, as discussed, we should implement some JSON (de)serialization interface for all the types. Maybe we should add an issue for this, so we don't forget?