add ConfKVS

[zeroXbrock]

ConfKVS is a distillation of suave's confidential storage primitives designed to radically simplify the process of creating and retrieving confidential storage records.
It always sets decryptionCondition to 0, so that records are always immediately available, because this is the most common usage, and removing a parameter is always nice.

Using it looks like this:

1. create a ConfStore

this should generally be stored by your SUAPP contract's constructor

ConfStore cs = ConfStore(addressList, addressList, "my_app_name");

2. set var

(this value also be stored in your SUAPP contract)

ConfRecord memory cr = cs.set("secretKey", abi.encodePacked("secret value"));

3. get var

bytes memory secretKey = cr.get();
assert(keccak256(secretKey) == keccak256(abi.encodePacked("secret value")));