Implement ability to ignore windows active for very brief periods

[TheCodeArtist]

Some apps implement notifications as custom windows that pop-up for a second or two,

Add the ability to choose to ignore logging any window that is active for less than a configurable threshold (in seconds).

[TheCodeArtist]

Implement in 2 phases:

• phase1: whenever logging a new active window, check immediate prev. logged window timestamp and delete prev. log if not older than threshold (2s)
• phase2: Make the threshold configurable from the GUI.