Support for Pagination (issue #496)

[tlienart]

Oh gosh finally...

Support for pagination, works like:

@def some_list = ["<li>$lc</li>" for lc in ("Stefan", "Jeff", "Alan", "Viral")]
~~~<ul>~~~
{{paginate some_list 2}}
~~~</ul>~~~

Assuming this is on page foo.md it will lead to

• /foo/ and /foo/1/ with content <li>Stefan</li><li>Jeff</li>
• /foo/2/ with content <li>Alan</li><li>Viral</li>

Note: this can be used with any sort of list or item, so it doesn't necessarily need to be a <li>... in fact it could be div blocks. More specific functionality can be wrapped in a newcommand e.g.:

\newcommand{\paginated_list}[2]{~~~<ul>~~~{{paginate #1 #2}}~~~</ul>~~~}

(will be a demo in FranklinFAQ)

closes #496

Note: if pagination over 5 pages then changing something and paginating over 2 pages, the dirs 3,4,5 will be removed. This should generally be innocuous with the exception of people who want to paginate their front page in which case it may be more likely to have numeric dirs in __site (but not very so probably still fine).