Archive page updates and Post Format title support

First off, my apologies for grouping all these into one pull request; I don't have much experience contributing to other repos. I didn't realize until now the commits were grouped under the cam pull request. In any case, all commits are related.

In short, I've added post format titles to the archive page via a function which defines the plural name for each supported post format. This same function is used to update the post format name in the wp_title filter. One last modification I did was swap the span tag in the archive table to wrap the heading descriptor text.