Create/implement smart contract for parameter setting

[BigLep]

Done Criteria

1. There is a deployed smart contract to Filecoin mainnet that complies with all constraints and requirements outlined in smart-contract based solution for Design a mechanism to reduce the need for two network upgrades for F3 activation to one #800
2. The source code for the smart contract is public

Why Important

This smart contract is the crux of a smart-contract-based solution #800, enshrining various rules and conditions for setting F3 activation parameters outside of a network upgrade.

User/Customer

F3 implementers who will use this contract to set F3 activation parameters.
Wider community for having visbility into the conditions in which the parameters can be set.

Notes

The exact requirements for this contract will be whatever is agreed in the output of #800