Adicionados métodos para eliminação de labels, cores e ícones (métodos "clear" e "reset", para vértices e arestas.
Adicionados métodos (API de C++):
bool GraphViewer::clearVertexLabel(int id)
bool GraphViewer::clearEdgeLabel(int id)
bool GraphViewer::clearEdgeColor(int id)
bool GraphViewer::clearVertexColor(int id)
bool GraphViewer::clearVertexIcon(int id)
bool GraphViewer::resetEdgeColor()
bool GraphViewer::resetVertexColor()
bool GraphViewer::resetVertexIcon()
bool GraphViewer::clearBackground()