refactoring, cleaning up, and adding docs
adding tests around AcceptCallback
making ballot udpate a method on EpaxosState, testing accept callback ballot update
adding tests around accept verb handler
adding tests around PreacceptCallback
adding tests around PreacceptVerbHandler
adding tests around CommitVerbHandler
removing gc grace seconds
adding tests around prepare callback and verb handler
fixed execution holdover from non-seda implementation
misc lock access & instance persistence updates