Added Finnish localization.

[SanteriHetekivi]

Here is the image of UI with Finnish translation on.

Some texts don't fit on buttons so they get cut, I have opened an issue (#164) for auto resizing buttons:

[SanteriHetekivi]

I changed "Pura Lattia" (Deconstruct Floor) to "Poista Lattia" (Remove Floor) commits.
"Poista Lattia" represents more closely the English translation.

I still like the Deconstruct Floor more because there is also Deconstruct Furniture, but for now I will keep same meaning text as in English version.

[SanteriHetekivi]

Updated from upstream/master and pushed typo fix.

[SanteriHetekivi]

Added translations for new fields:

furn_airlock=Ilmalukko
furn_airlock_desc=Ilmalukko estää ilman karkaamisen tukikohdasta.
tile_Empty=Tyhjä
tile_Empty_desc=Tyhjä laatta.
tile_Floor=Lattia
tile_Floor_desc=Täyttää korkeimmat liukastumisen esto standardit.

[SanteriHetekivi]

Added translations for new fields:

furn_metal_smelter=Metallin Sulatusuuni
furn_metal_smelter_desc=Sulattaa raa'an rautasi metalliksi.