the idea is that an invoker holds a weak_ptr to a steppable. and
anything with an invoker can advance a steppable
app::add_sort has become too heavy because of the way timer and
invoker are initialized now.
App now adds already constructed Timers
Timer is now an Invoker that takes a weak_ptr to a steppable with a
request()rather than a bool callback.
should eventually be changed to composition
reduced responsibilities of constructors
started using more pointers.
sessions through app rather than app itself.
mostly split view away from app (still hard coded)
haven't decoupled sorts from timers as their actuator yet
couldn't figure out how to handle sortstate, eventually put it into
bsort class. should be split into timeraction and steppable. and there
shouldn't be a random steppedbsort in App
lyrgb