Forward Graphs.jl access functions to Mango topology

[jsagerOffis]

Mango.Topology should forward Graph.jl access functions for easier use.

Example desired behavior:

using Mango
x = complete_topology(5)
nv(x)
> 5

This would save many calls to x.graph and should be very easy to implement. Reference list of access functions for Graph.jl:

https://juliagraphs.org/Graphs.jl/dev/first_steps/access/

[jsagerOffis]

For reference:

Graphs.dst Graphs.edges Graphs.edgetype Graphs.has_edge Graphs.has_vertex Graphs.inneighbors Graphs.is_directed Graphs.ne Graphs.nv Graphs.outneighbors Graphs.src Graphs.vertices