allowance lists for AMB extensions

[akolotov]

Consider to add functionality to add and remove extensions that can be allowed to use AMB to transfer information from one chain to another.

The allowance list should work in the following manner: if at least one mediator address is added to the allowance list, the call requireToPassMessage to AMB from all other contracts will lead to revert.

Interface to add remove contracts from the list should allow to specify one contract address or the list of the contract addresses.