class PeriodicalExecuter
Description
A class that oversees the calling of a particular function periodically.
PeriodicalExecuter
shields you from multiple parallel executions of the
callback
function, should it take longer than the given interval to
execute.
This is especially useful if you use one to interact with the user at given intervals (e.g. use a prompt or confirm call): this will avoid multiple message boxes all waiting to be actioned.