Add warning boxes to draw attention to the instrument and archive manuals

[barentsen]

The following pages could do with a loud information box at the top to point out that more detailed information is contained in the instrument/archive manual:

• http://keplerscience.arc.nasa.gov/the-kepler-space-telescope.html
• http://keplerscience.arc.nasa.gov/data-products.html
• http://keplerscience.arc.nasa.gov/pipeline.html