ENH: Implement stopLogging method for YVBKeyLogger

The method was not implemented and it internally would just change the
value of the isLogging property.

The key logger now stops the active run loop and inactivates the event.
ENH: Stop logging when loading data for display

With the recent implementation of the isLogging method in the
YVBKeyLogger class we can now stop the keylogger while the appplication
is busy loading the information for display on the main screen. Doing it
otherwise would stack up threads and eventually make the application
unresponsive.

In summary:
    - The key logger object is now a property of the application
      delegate.
    - Since the completion of the collected information is asynchronous,
      we use _startLogger to check whether we have retrieved all the
      needed information and if we can start listening to the key logger
      again.
    - A few properties had the following declaration
        ClassBar __block *foo;

      Which has been changed to be:
        __block ClassBar *foo;

      This does not affect the declaration of the variable, but is the
      standard way to do it (or so I have seen online).
MAINT: Change daily executor internals

The YVBDailyExecutor class no longer relies on a single NSTimer that is
meant to be executed at midnight, instead it now checks every five
minutes and compares whether or not the current date (from which it was
initialized) has changed, if this is true then it updates the current
date and repeats.

I have also removed the subscription to
NSSystemClockDidChangeNotification because this made the system execute
the handler block whenever the computer went to sleep and whenever the
computer awoke.

The main reason to do this and not using NSTimer and subscribing to the
sleep/awake notifications to account for the time changes is because we
would still need a notification when the system clock changed however,
this notification got triggered every time there was a sleep/awake event
which was pointless.
ENH: Perform daily executor task in a 2nd thread
BUG: Reset the logger the main NSThread

If we do this using GCD and main_queue, we get an unexpected behaviour
that locks the app and as soon as keystrokes start coming in, they start
pilling up and never return, until the point where the app crashes.