remove default constructors for Node and Edges

alib2algo/src/graph/shortestpath/BellmanFord.cpp

alib2algo/src/graph/shortestpath/Dijkstra.cpp

alib2algo/src/graph/spanningtree/JarnikPrim.cpp

alib2algo/src/graph/traverse/Bfs.cpp

alib2algo/src/graph/traverse/Dfs.cpp

alib2algo/test-src/graph/spanningtree/JarnikPrimTest.cpp

alib2algo/test-src/graph/traverse/BfsTest.cpp

alib2algo/test-src/graph/traverse/DfsTest.cpp

alib2data/src/graph/common/Node.cpp

alib2data/src/graph/common/Node.h

alib2data/src/graph/directed/DirectedEdge.cpp

alib2data/src/graph/directed/DirectedEdge.h

alib2data/src/graph/undirected/UndirectedEdge.cpp

alib2data/src/graph/undirected/UndirectedEdge.h

alib2data/test-src/graph/GraphTest.cpp