Add "next" and "previous" page navigation to the gitbook documentation

[morrowcj]

The online documentation for SWAT+ is great but would benefit from page navigation buttons. Currently, to navigate to the next page, one needs to click on the table of contents. A more useful method would be to have a "next page" (and "previous page") or "next section" button at the bottom or side of each page:

[tugraskan]

Thanks for the suggestion the SWAT + gitbooks is currently separate from this repo, but we are working on updating it and I see if we can implement your suggestion.

[morrowcj]

Thanks for the suggestion the SWAT + gitbooks is currently separate from this repo, but we are working on updating it and I see if we can implement your suggestion.

Oh, sorry about that. Can you direct me to the repo that houses the gitbook? Or is it not on github?