Asynchronous information receiving by an AMB extension

[akolotov]

This issue is to address the changes needs to be done in the AMB contracts to allow AMB extensions to send requests to the bridge oracles to read information from another chain.

Preliminary call flow:

1. A mediator invokes a new method from the AMB contract (e.g. requireToGetInformation), specifies the contract and the ABI encoded message to be executed on the Foreign chain and the contract on the Home chain that will expect the answer -- result of the message call.
2. The oracles receives a new event raised by the bridge contract.
3. The oracles calculate the block in the Foreign chain to make eth_call by using the timestamp of the transactions with the data request.
4. The oracles executed the encoded message on the contract
5. The oracles pass the received result to the contract recipient.

The changes made under this issue should be for the direction Home->Foreign.