Conv no bias

• Add noBias for Conv & ConvDepthWise (and underlying MetaOperator)
• Add GraphView.logOuputs method to allow better debug

Minor modifications

• toString is now a virtual function of Data.

include/aidge/data/Data.hpp

@@ -52,6 +52,7 @@ public:
         return mType;
     }
     virtual ~Data() = default;
+    virtual std::string toString() const = 0;
 
 private:
     const std::string mType;
@@ -84,4 +85,4 @@ namespace Aidge {
 inline auto format_as(DataType dt) { return EnumStrings<Aidge::DataType>::data[static_cast<int>(dt)]; }
 }
 
-#endif /* AIDGE_DATA_H_ */
\ No newline at end of file
+#endif /* AIDGE_DATA_H_ */