Hadrons: much simpler reference dependency

extras/Hadrons/Modules/MGauge/Unit.cc

@@ -47,6 +47,13 @@ std::vector<std::string> TUnit::getInput(void)
     return std::vector<std::string>();
 }
 
+std::vector<std::string> TUnit::getReference(void)
+{
+    std::vector<std::string> ref = {};
+    
+    return ref;
+}
+
 std::vector<std::string> TUnit::getOutput(void)
 {
     std::vector<std::string> out = {getName()};

extras/Hadrons/Modules/MGauge/Unit.hpp

@@ -50,6 +50,7 @@ public:
     virtual ~TUnit(void) = default;
     // dependencies/products
     virtual std::vector<std::string> getInput(void);
+    virtual std::vector<std::string> getReference(void);
     virtual std::vector<std::string> getOutput(void);
 protected:
     // setup