Added datasets source file and updated associated files.

[elk2klein]

• The datasets browse page does not work - nothing under the header shows up. Maybe something with faceting script or styles in datasets.html? The items show up in the search, and I am able to access them with their permalinks and through the search.
• I manually edited index.json and datasets_only.html to see if the pages themselves worked (they did), so will need to go back and edit files that contribute to those (as in, the files that tell the pages wax task to include certain metadata fields like layout, config file, etc.).
• I also updated some documentation.