Wasser 1.6.4

Wasser 1.6.4: Added manual Temperatur setting set_temp for debug
reasons. Added default option in texts.php. Seperated off season
display in new file.
Core 1.4: Support for valid and standard encoded XML for support of
external Services like IFTTT. Core is able to tweet current temperature
by itself and doesn't rely on external services any more. XML entry is
only created if one item has changed, to safe resources.