Tidy up whitespace and trailing space.
Generate timestamp files to one-hour precision.

When this runs on multiple machines, one machine may generate a
different filename from another, causing broken links to sitemap files.
Run the generation task shortly past the hour.

This sidesteps the problem where multiple boxes could potentially run on
the cusp of the hour and generate different timestamps.
Merge remote-tracking branch 'origin/fix-sitemap-timestamps'