The Ownable contract has an owner address, and provides basic authorization control functions, this simplifies the implementation of "user permissions".
event OwnershipTransferred(address previousOwner, address newOwner)
Throws if called by any account other than the owner.
function Ownable() public
The Ownable constructor sets the original `owner` of the contract to the sender account.
function transferOwnership(address newOwner) public
Allows the current owner to transfer control of the contract to a newOwner.
newOwner- The address to transfer ownership to.