Add new data page for displays

Show latest data histograms and barometer data for given station.
If station does not have weather, get it from other station, closest by
number.
Resizes to fit on screen, currently expects 1280x750, need something
nicer.
Show clearly if data is older than yesterday.
Add live (current) status indicator.
Add status and auto refresh. Improve zoom and no data.

Add Nagios status indicator
Refresh page every 10 minutes if there is no activity
Improve widths/padding and zooming
Show text to show no data is available
Remove some unneeded lines of code
Merge pull request #52 from HiSPARC/latest-data-page

Add 'latest' data page to show histograms,
in a way more suited for wide displays.