fi: Fixes TTS talking about meters_metria, other improvements to phrasing

The current Osmand beta in Google Play has a serious issue in Finnish TTS where it says something like "100 meters underscore metria" when it should only say "metriä". I hope I finally figured out why: The language file was using different strings in the definition and actually constructing the phrases, so my guess is TTS was just reading the names of the non-existent ogg files provided as strings in the prolog file. Now they should match (see lines 273 onwards).

There was also some use of 'reached.ogg' which was not defined at all (around line 197). I copied the version without that from the English language file.

I did run this through prolog (with gen_voice.sh) and it went without errors, but I haven't really figured out how to test it locally on my phone, so code review is explicitly requested to ensure I haven't funked up something even more. Let me know if there is an issue.

In addition, I improved on some of the remaining linguistic oddities.