Refactor eth block handler to follow architectural principles

[filo87]

ethHandlers.ts should be refactored to adhere with the following principles:

• Handlers should contain no direct assignment of Entity values. State alterations must be performed through appropriate Service methods (such as PoolService.ts or LoanService.ts)
• Avoid use of array iterators methods such as .map() or .foreach() in combination with async functions, as these can lead to the raising of unhandled exceptions. Use for ... of ... instead.
• Refactor contract calls to be included in the appropriate Service Method