Replaced function pointer with std::function

Changed function container from set to vector. Set requires
implementation of operators not found in std::function.

Std::function supports function objects for greater flexibility.
Renamed Monitor class to Event Handlers

As part of moving to a multi-threaded program structure, I have renamed
Monitors to Event Handlers. Event detection has been removed as part of
the specialization of the Event Handlers template.
Initial commit of Event Queue class
Removed "do-not-block" for ncurses KB input
Updated for multithreading support