Add support for artist aliases

Use MusicBrainz artist aliases to import files with artist names in an
appriorate locale
Merge pull request #102 from samdoshi/aliases

Add support for artist aliases (fixes GC-354)
refactor alias discovery into function (#102)
change option name to "languages"; docs (#102)
link to GitHub Issues
import.detail config option (GC-263)
add --flat option to import command (GC-202)