Doc: add images and references

Documentation/Images/black_dot.png

Documentation/Images/blue_dot.png

Documentation/Images/bulb.png

Documentation/Images/bullet-blue.gif

Documentation/Images/bullet-gray.gif

Documentation/Images/bullet-green.gif

Documentation/Images/bullet-pink.gif

Documentation/Images/bullet-red.gif

Documentation/Images/bullet-yellow.gif

Documentation/Images/checkboxinvert.gif

Documentation/Images/checked-blue.gif

Documentation/Images/checked-gray.gif

Documentation/Images/checked-green.gif

Documentation/Images/checked-pink.gif

Documentation/Images/checked-red.gif

Documentation/Images/checked-yellow.gif

Documentation/Images/construction.gif

Documentation/Images/copy.gif

Documentation/Images/delete.gif

Documentation/Images/down.gif