Simplified network_graph to provide a better bird's eye view of network
structure.
Initialized R, G, B, GR in mint_network_camera
Turned sparse inot an op, not a keyword anymore
Added type arguments to mint_op_new, mint_op_find, and others so that
ops with the same name but different type do not clash. This is a bit
cumbersome in the code (although generic types like mint_op_nodes_any
help) but hopefully transparent to the user