addValidator refactoring

[lorien]

I suggest to split addValidator on two functions:

• function that handles request from voting key (add or update data)
• function that handles request from initial key (add data)

Also I suggest to move mining key data existence check into separate method. Something like:

function isMiningKeyDataExists(address miningKey) returns (bool) {
    bytes memory name = bytes(validator[miningKey].fullName);
    return name.length > 0;
}

[vbaranov]

See https://github.com/oraclesorg/oracles-contract/commit/1e7f00a6a81a72da0215ed3c2f863ae4823570e4 + https://github.com/oraclesorg/oracles-contract/commit/3a065ecdf31d2157dc3a501140edd1d36b206c0b