annotation && v2proxy add gasreturn and trade incentive && proxyV2 incentive test

contracts/DODOVendingMachine/impl/DVM.sol

@@ -14,6 +14,12 @@ import {DVMTrader} from "./DVMTrader.sol";
 import {DVMFunding} from "./DVMFunding.sol";
 import {DVMVault} from "./DVMVault.sol";
 
+/**
+ * @title DODO VendingMachine
+ * @author DODO Breeder
+ *
+ * @notice DODOVendingMachine initialization
+ */
 contract DVM is DVMTrader, DVMFunding {
     function init(
         address maintainer,
@@ -76,6 +82,7 @@ contract DVM is DVMTrader, DVMFunding {
     }
 
     // ============ Version Control ============
+    
     function version() external pure returns (string memory) {
         return "DVM 1.0.0";
     }

contracts/DODOVendingMachine/impl/DVMFunding.sol

@@ -40,11 +40,10 @@ contract DVMFunding is DVMVault {
         quoteInput = quoteBalance.sub(quoteReserve);
         require(baseInput > 0, "NO_BASE_INPUT");
 
-        // case 1. initial supply
-        // 包含了 baseReserve == 0 && quoteReserve == 0 的情况
-        // 在提币的时候向下取整。因此永远不会出现，balance为0但totalsupply不为0的情况
-        // 但有可能出现，reserve>0但totalSupply=0的场景
+        // Round down when withdrawing. Therefore, never be a situation occuring balance is 0 but totalsupply is not 0
+        // But May Happen，reserve >0 But totalSupply = 0
         if (totalSupply == 0) {
+            // case 1. initial supply
             require(baseBalance >= 10**3, "INSUFFICIENT_LIQUIDITY_MINED");
             shares = baseBalance; // 以免出现balance很大但shares很小的情况
         } else if (baseReserve > 0 && quoteReserve == 0) {

contracts/DODOVendingMachine/impl/DVMTrader.sol

@@ -35,7 +35,7 @@ contract DVMTrader is DVMVault {
         uint256 quoteAmount
     );
 
-    // ============ Execute ============
+    // ============ Trade Functions ============
 
     function sellBase(address to)
         external

contracts/DODOVendingMachine/impl/DVMVault.sol

@@ -179,6 +179,7 @@ contract DVMVault is DVMStorage {
     }
 
     // ============================ Permit ======================================
+    
     function permit(
         address owner,
         address spender,
@@ -205,5 +206,4 @@ contract DVMVault is DVMStorage {
         );
         _approve(owner, spender, value);
     }
-    // ===========================================================================
 }