doxygenate Command, flesh out Command, add Sleep to System

Command:
    Reorder destructor
    Segregate killing to KillProcess function
    Switch special statuses to an enum class
    Clean up constructor, and add ability for timeout seconds
    Read in buffered (still does nothing)
    Kill sets a special status
    There is a RUNNING Status
    Children are killed in a process group now
    pselect is used to prevent children from hanging pipes