Date range with weather and telemetry lookup

I'm on a 2-week sick leave (my gallbladder was removed last week), and have some spare time for enhancements and bug fixes. Rest of the time I'm entertaining Armi the cat, who joined us on Friday.

This morning I added arbitrary date range lookups to the weather and telemetry pages. It allows you to look up a detailed graph between any two dates or times. It also has a little calendar widget for your convenience.

I've also done some XHTML validity fixes for better browser compatibility, switched to a smaller position marker on the static maps, and added some navigation links in the bottom of most pages. I also fixed the bug of date selection menu not appearing when clicking on 'start tracking' on the live map.

Also, the /info/ page of a weather station now shows a brief 'latest weather' report instead of the number of weather reports in database. It's probably much more interesting, and it's much quicker to load, too, since it's almost always cached in memory and doesn't require a potentially large disk read.