Deposit: Allow integrators to specify % of yield to be paid to them on deposit call

As more integrators start using Aave, provide the ability for the integrator to charge a fee on the yield earned from the deposit.

I.E: Customer A uses an integrator to deposit $1m USDC at a yield of 2%.

The integrator would like to receive 0.05% of the yield earned to their ethereum address. When the customer withdraws their deposit, the integrator is paid the fee to their account and the remainder of the yield including the deposit is returned to the deposit address.

Update the “deposit” call to include two new optional parameters:

function deposit( address _reserve, uint256 _amount, address _feeAddress, unit256 _feeAmount)

This can allow 3rd parties providing integrations to Aave to receive a fee for providing the service.

Note: I am not sure what impact this has on the aToken and what happens to the fee if the aToken is transferred to another party. Open to suggestions.

As this is my first proposal, happy for input of any type!