Implement previous/next/first/last links

Here's a patch implementing the previous/next/first/last links. This patch enables the option of having pagers in view's feed display.The user can click to enable mini or full pager for the view and get the same result (Not completely happy with that part, but it's the best I could think of with views and works well).

Here's an example:

  <link rel="first" href="http://nhlocal.com/atom?page=0" />
  <link rel="last" href="http://nhlocal.com/atom?page=189" />
  <link rel="previous" href="http://nhlocal.com/atom?page=18" />
  <link rel="next" href="http://nhlocal.com/atom?page=20" />
  <updated></updated>
  <link rel="self" type="application/atom+xml" href="http://nhlocal.com/atom?page=19"/>