Minor changes, changed how QSnapper functions.

QSnapper now has the option to allow "slightly different" images, so
things like a blinking text cursor won't create a new image. The
threshold for new images is that the pixels changed must be more than 1%
of the display's pixels: (width * height)/100.

Also added the ability to view "difference images", where the
differences between two images are drawn on top of a light blue, so you
can see exactly what changed, if it seems like two images are identical.
Added Support for QT5's connect() syntax, currently it is ifdef'd based
on what version of Qt is running. Also removed the disconnect() calls as
everything is disconnected when destroyed, so they were unneeded.
QSnapper now asks if the screensaver is active and, if so, does not take
a picture. This is tested on Linux via D-Bus, and an implementation is
provided for Windows, but it is not yet tested.
Added documentation to a function that was missing it. Removed Generated
html, as it can easily be generated locally with "doxygen Doxyfile"