Whew.  Well, that's a good nights work I think.  Cities are...well...
they're there.  As a proof of concept, they work, although they are hella
uncomfortable to explore.  And kind of boring.  I should make the streets
wider. It's also very difficult to get a sense of what's where.  Some things
to note:
-I upped the chunk size, which is breaking deserialization for some reason
-To play as normal, lower the chunk size back down in src/constants.h and
 comment out the last few lines of src/world/overworld_gen.cpp