feat: removing singular name functions and changing them to plural naming

[MarIniOnz]

Removed functions:

• add_node
• add_edge

Renamed functions:

• remove_node -> remove_nodes
• remove_edge -> remove_edges
• remove_group -> remove_groups
• add_node_to_group -> add_nodes_to_group
• add_edge_to_group -> add_edges_to_group
• remove_node_from_group -> remove_nodes_from_group
• remove_edge_from_group -> remove_edges_from_group

For testing, a make install-dev action is required!