initial attempt for initContract

[rbaconcordium]

Purpose

to deserialize TransactionPayload.InitContract

Changes

implemented deserialize function within accountTransactions.ts for InitContractPayload

Checklist

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

[soerenbf]

Looks like you need to set up your formatter? 😉