Allow for imports of "primary" classes directly from uavf

[rland93]

I like what NetworkX does with their classes.

We import the top-level

import networkx as nx

And then we can access the useful networkx classes and functions from this top-level module. For example:

import networkx as nx
G = nx.Graph()
nx.add_path(G, [0, 1, 2])
nx.add_path(G, [0, 10, 2])
print(nx.all_shortest_paths(G, source=0, target=2)]))

We don't need to do like

from networkx.algorithms.shortest_paths import all_shortest_paths

Every time we want to grab a function.