#361 Updated Finnish translation

[Sampo Hippeläinen]

• Updated to 19.00, doesn't seem too much has changed, but a few strings might have (or maybe they were translated from even earlier versions?)
• Alternate streams to "Vaihtoehtoiset virrat", the translation Microsoft uses
• "Type" in "Select by Type" = "Tyyppi", since it means file type and that is "tiedostotyyppi", not "tiedostolaji"
• "Documents" from "Dokumentit" to "Asiakirjat", again used by Windows and most other operating systems as well
• "Non-solid" to "Irrallinen" (literally "separate", as the files are compressed separately)
• Background and Foreground to "Aja taustalla" and "Aja edustalla", which are closer to the English translations and describe what they do better (at least in my opinion)
• Some other minor changes

Since I kept most of the existing translations, I only added myself as a translator to the existing list.