blog: Refactor entry rendering into a partial.

This helps ensure that entries are rendered consistently wherever they
appear.

blog: Display tags with dateline.

This hopefully makes it a little clearer which entry the tags apply to.

blogs, news: Don't shade entries on listing pages.

This just causes entire pages to be shaded, which is undesirable.

Correct navigation links.

Earlier commit incorrectly implemented navigation link suppression when
only one page present, such that this was never shown. This is now
corrected herein.

Restore navigation links.

Previous commit incorrectly implemented solution for avoiding showing
nav links. This corrects that.

Move blog index to be part of base template.

This way, it's not on the bottom of pages. This shouldn't cause
trouble, since when date_list isn't defined, nothing is shown by this
code.

Typo fix.

<tmarble> also blog left nav is borked [15:11]

Rework blog's custom_index for new pagination.

The pagination support changed, and as was previously done a few commits
ago for news, I'm trying a similar solution for blogs.

In this case, I'm trying to use the existing custom_index() method we
have and adapt it to properly support pagination in the way we want.

I'm not completely sure this will work, but I think it's at least close.