The design of the signature table.

[lychees]

    // @abi table signs
    struct sign_info {
        uint64_t id;
        account_name creator = 0;
        account_name owner = 0;
        uint64_t creator_fee;
        uint64_t ref_fee;
        uint64_t k;        
        uint64_t price;
        uint64_t last_anti_bot_fee = 0;
        uint64_t anti_bot_init_fee;
        time anti_bot_timer;
        time last_buy_timer;        
        time st;
        uint64_t primary_key()const { return id; }
        uint64_t next_price() const {
            return price * k / 1000;
        }
    };    

Involve UGC (User generator content) is a key part in dapp design. In Smart Signature, every independent user can upload his own article and issue his own signature on the top of it. And of course, according to our slogan ("Give the power back to users!"), we should also trust and give our users as much freedom as possible to make their own choices.

The user can choose:

• s.creator_fee = 20, how many fee will be charge each time when some one sponsor the article, in ‰, by default it is 2%.
• s.ref_fee = 50, how many fee can be reward to the referrer, in ‰, by default it is 5%.
• s.k = 350, how fast the price will be increase in each time someone buy the signature, in ‰, by default, the new price shall be calculated as 1.35 times the last signature price.
• s.price = 1000, the initial price of the signature, by default it is 0.1 EOS.
• s.st = now(), the start time of the auction.

yukiexe@, would mind to help me to:

• [x] Implement the remain part of the sign::sponsor() function when there is a referral.
• [x] Implement the remain part of the sign::create() funciton.

Don't forget to examine the boundary conditions for each of them.

• 0 <= s.ref_fee <= 500
• 10 <= s.k = 1000
• 1000 <= s.price = 10000000
• now() <= s.st = now() + 3652460*60