weather: forecast up to 10 days

* plugin needs an APIKEY to be registered

* display temperatures of day and night,
  average wind and txt summary

* posibility to specify date
  if no date specified, current one is used

* if location is not in service's db, use gps pos

Signed-off-by: Adrian Matejov <a.matejov@centrum.sk>
Merge pull request #34 from Adman/weather

weather: forecast up to 10 days