systemcontract: change register fee and exit fee rate

[txhsl]

Relate #247, #236 and #271.

Increase the exit fee rate from 5% to 50%, but decrease the register fee from 20000 GAS to 2000 GAS, which is suggested by @steven1227 for mainnet configuration.

NOTE: Genesis allocation is not updated here.

[AnnaShaleva]

I think 50% is really a lot, this logic seems to be imbalanced a bit with this value. Do you have a reason of why the charge is so large?

[txhsl]

I think 50% is really a lot, this logic seems to be imbalanced a bit with this value. Do you have a reason of why the charge is so large?

Well, the code expression of 50% seems quite rude, so I changed it a bit. Let me describe the background first.

1. N3 charges 1000 GAS for registration, and it will not be refunded;
2. The first Neo X solution refunds all register fee back;
3. I'm not expected to change the registration logic after audit;
4. We need an exit fee there to prevent DoS attack about candidate limit, and we expect it to be the same amount of N3;
5. The 20000 GAS deposit is too much (comparing with 32 ETH on Ethereum), and market requires us to lower it;

How about now? I declare the exit fee as a fixed value.

[roman-khimov]

Is it that much different from N3 "pay 1000 GAS and never worry again)" model then?

[AnnaShaleva]

To be honest, the previous rate-based way was more preferable to me because fee is always proportional to the deposit which seems to be honest and protective from DoS for every deposit value. The question from my side was why 50%. But from your answer I see that it's a necessity, thus may be it's OK to keep 50%.

[txhsl]

Is it that much different from N3 "pay 1000 GAS and never worry again)" model then?

To have the same thing as N3 “pay 1000 GAS and never worry again” model, I will have to change the register and exit logic here. But I don't expect that after audit, especially closely before mainnet.