Chainparams: CTestNetParams and CRegTestParams extend directly from CChainParams

...instead of CMainParams and CTestNetParams respectively

Do the same for CBaseChainParams.
The inheritance was only reducing readibility in this case

src/chainparamsbase.cpp

@@ -25,7 +25,7 @@ static CBaseMainParams mainParams;
 /**
  * Testnet (v3)
  */
-class CBaseTestNetParams : public CBaseMainParams
+class CBaseTestNetParams : public CBaseChainParams
 {
 public:
     CBaseTestNetParams()
@@ -39,11 +39,12 @@ static CBaseTestNetParams testNetParams;
 /*
  * Regression test
  */
-class CBaseRegTestParams : public CBaseTestNetParams
+class CBaseRegTestParams : public CBaseChainParams
 {
 public:
     CBaseRegTestParams()
     {
+        nRPCPort = 18232;
         strDataDir = "regtest";
     }
 };