FLAC stores tags on track level. Hence we must parse the
tracks here in order to parse the tags. This hasn't been taken
into account when refactoring the tag editor CLI leading to
https://github.com/Martchus/tageditor/issues/36.
So let's handle these format specific details in the tagparser
library which will now internally parse tracks when calling
parseTags() on FLAC files.
This also fixes the weird behavior to consider tags supported
although the container format is unknown.
Martchus