Graph generator for biqmac-rudy files

[CharJon]

The biqmac lib has a rudy section.
We want to be able to generators instances of the same type (g05, pm1s, pm1d, wd100, pwd01, t2gn).
Each type should have its own function, but they are quite similar and should call some common background functions. All weights are integer and the function should accept and optional bool "keep_zero_edges"=true. If the parameter is set to false, edges with zero weight should not be added to the graph.