Make dates a lot less redundant.

Drawing the date from the filename instead of repeating it four times
sure is nice.

Prior to this the date of the post was defined:
1. in the filename in DB-style format
2. in the filename in long form
3. in the front-matter data metadata
4. in the post title

Now it's only defined in the filename because it makes sense.

I also changed the permalink settings to put year/month/date instead
of month/day/year because the latter's just silly.
Convert second post to new date settings.