mosquitto needs a lot of attention concerning its config because it doesn't
parse it very well, often ignoring trailing parts of lines, duplicated config
keys, or just looking back way further in the file to associated config keys
with previously defined items than might be expected.
this replaces the mosquitto module completely. we now have a hierarchical config
that flattens out to the mosquitto format (hopefully) without introducing spooky
action at a distance.
