Updated deprecated dependancies of package.json and added new contract

[inesgoldschmidt]

Updated package.json dependencies and added new contract AppCoinsTracker

Description

Went through the dependencies in package.json and updated the deprecated ones and checked if everything was still working as is should.

Motivation and Context

Grantees that the contracts aren't using deprecated dependancies.

How Has This Been Tested?

Tested through truffle test and also other python tests. The python tests where made only for the contracts that are currently in use (AppCoins, AppCoinsIAB, AppCoinsTracker, AddressProxy).

Screenshots (if appropriate):

Checklist:

• You have followed our contributing guidelines
• double-check your branch is based on dev and targets dev
• Pull request has tests (at least 80% coverage)
• Code is well-commented, linted and follows project conventions
• Documentation is updated (if necessary)
• Description explains the issue/use-case resolved and auto-closes related issues