Creates a catNetwork object from list of nodes and edges.
cnCatnetFromEdges(nodes, edges, numcats=2)a vector of node names
a list of node edges
an integer, the number of categories per node
A catNetwork object
The function uses a list of nodes and directional edges to create a catNetwork with specified (fixed) number of node categories.
A random probability model is assigned, which can be changed later by cnSetProb for example.
Note that cnSetProb takes a given data sample and changes both the node categories and their conditional probabilities
according to it.