Switch testing framework from MAIN to new UNITTEST network

UNITTEST inherites from MAIN but allows synamically changing its parameters using the ModifiableParams() interface

src/chainparams.h

@@ -61,6 +61,8 @@ public:
     bool DefaultCheckMemPool() const { return fDefaultCheckMemPool; }
     /* Allow mining of a min-difficulty block */
     bool AllowMinDifficultyBlocks() const { return fAllowMinDifficultyBlocks; }
+    /* Skip proof-of-work check: allow mining of any difficulty block */
+    virtual bool SkipProofOfWorkCheck() const { return false; }
     /* Make standard checks */
     bool RequireStandard() const { return fRequireStandard; }
     int64_t TargetTimespan() const { return nTargetTimespan; }
@@ -105,6 +107,24 @@ protected:
     bool fMineBlocksOnDemand;
 };
 
+/** Modifiable parameters interface is used by test cases to adapt the parameters in order
+*** to test specific features more easily. Test cases should always restore the previous
+*** values after finalization.
+**/
+
+class CModifiableParams {
+public:
+    // Published setters to allow changing values in unit test cases
+    virtual void setSubsidyHalvingInterval(int anSubsidyHalvingInterval) =0;
+    virtual void setEnforceBlockUpgradeMajority(int anEnforceBlockUpgradeMajority)=0;
+    virtual void setRejectBlockOutdatedMajority(int anRejectBlockOutdatedMajority)=0;
+    virtual void setToCheckBlockUpgradeMajority(int anToCheckBlockUpgradeMajority)=0;
+    virtual void setDefaultCheckMemPool(bool aDefaultCheckMemPool)=0;
+    virtual void setAllowMinDifficultyBlocks(bool aAllowMinDifficultyBlocks)=0;
+    virtual void setSkipProofOfWorkCheck(bool aSkipProofOfWorkCheck)=0;
+};
+
+
 /**
  * Return the currently selected parameters. This won't change after app startup
  * outside of the unit tests.
@@ -114,6 +134,9 @@ const CChainParams &Params();
 /** Return parameters for the given network. */
 CChainParams &Params(CBaseChainParams::Network network);
 
+/** Get modifyable network parameters (UNITTEST only) */
+CModifiableParams *ModifiableParams();
+
 /** Sets the params returned by Params() to those for the given network. */
 void SelectParams(CBaseChainParams::Network network);