path: Only accept bytes as paths
path: Ensure mopidy.__main__ uses bytes for paths
config/path: Pass in expanded value in expanded path type
path: Disallow unknown substitutions in expand_path
local: Do not create missing media/playlists dir
scanner: Handle missing media_dir
path: Update with respect to review comments in #427
Merge pull request #427 from adamcik/feature/path-as-bytes

Enforce that we only want bytes in path related code.