Updates for layout and adds fdp header to data pages

content/contributing/_index.md

content/contributing/how.md

content/fdp/jupiter.md

content/fdp/mars.md

content/fdp/mercury.md

content/fdp/moon.md

content/fdp/neptune.md

content/fdp/pluto.md

content/fdp/saturn.md

content/fdp/smallbodies.md

content/fdp/uranus.md

content/fdp/venus.md

content/metadata/_index.md

content/supplemental/_index.md

layouts/shortcodes/data-table-header.html