Currently, pretty-printing for choicemaps does not attempt to sort the addresses of leaf-nodes or submaps before printing them:

This leads to confusing output for choicemaps produced by the dynamic modeling language, especially those that involve for loops -- the addresses are not sorted by timesteps, and so it's not as easy to parse what's in the choicemap.

Fixing won't be hard -- we just need to sort the keys before printing, taking care to handle addresses which don't have ordering functions (Base.:<) defined for them.