Updated pywws.Template documentation.
Use stored timestamp & ptr to avoid duplicate data.

This should cure Brett Hoyle's interesting "duplicate data after a
reset" problem without breaking anything for those stations that do
reset the data count and pointer when the station is powered down.
More tweaking of 'live logging' sync algorithm.
Another live log sync algorithm tweak.
Add more info to 'unexpected sensor clock change' message.
Reverse small change made in commit b8723c553c.

When a data pointer increment is detected there may already be new live
data at the new address, but it's not dtected as soon as it might have
been. This change ensures we don't reset the 'sensor clock' as a result
of this change.
Updated change log.
Added 'low_battery' status.

I've recently found out that the outside sensors send a 'low battery'
warning by setting bit 7 of the 'wind direction' byte. I've modified
pywws/WeatherStation.py to tack this on to the existing 'status' value
as bit 11.
On my weather station this status seems to be set for short periods
quite often. I think it's only meaningful if it stays on for days.
New reprocess script, with option to update status.

The '-l' option reinterprets the old raw data to extract the 'low
battery' status added in commit 0eaf9dd4a5. You only need to use this
option once, and don't actually need to do it at all.
Undo supposed 'low battery' status changes.

The commits 0eaf9dd4a5 and 5142f38708 were based on a misunderstanding
about bit 7 of the 'wind_dir' byte. This commit corrects that mistake
and adds an 'invalid wind dir' status bit. If you reprocessed your data
after commit 5142f38708 you need to reprocess it again. Otherwise,
reprocessing is optional.
Added note about disabling hourly.
Stop pywws.Upload repeating error messages.
Stopped immediate retries if uploads fail.

If the network's down there's no point retrying immediately. Live
logging will retry soon enough, hourly will retry the next time it's
run.
Updated documentation of pywws.toservice
Removed duplicate service templates.

In some cases the 3080 and 1080 type templates are identical.
pywws.toservice now uses the 1080 template if there isn't a 3080 one.
Added service config to set minimum data interval.

Some services specify a minimum interval between weather records (e.g.
the UK Met Office says records should be at least 15 minutes apart). The
new config item specifies this interval in seconds.
Made params and status storage threadsafe.
Changed how tasks are passed to asynchronous thread.

Separate queues are used for each type of task (twitter, service,
upload). The same queues are used in non-asynchronous mode so this now
gets the benefit of doing no more than 50 service uploads at a time.
Improved toservice handling of 'last update' times.
Moved urlencoding of data.