Renamed reference to mainloop to main
Added clone-propn-net
In make-person wrapp propn-net in clone-propn-net

i.e. it's OK to pass an old propn-net to make-person now, because
make-person will automatically create a "new" propn-net, i.e. one
with its own copy of the weight matrix passed in.
Added call to reset! folks in init
Now creates 3 persons, inits pop, creates pop lazyseq