complete greek translation

- translate all remaining entries
- remove fuzzy translations
- modify some entries with terms from the Hellenic National
  Meteorological Service
  http://www.hnms.gr/hnms/greek/meteorology/full_story_html?dr_url=/docs/lexikon/lexicon&dr_page_number=1

Signed-off-by: George Boumis <developer.george.boumis@gmail.com>