Scanner: Fix deadlock on incorrectly identified files
Throw an error when scan_timeout config is not loaded.
docs: Document local/scan_timeout config value
scanner: Fix local/scan_timeout value check
scanner: Fix unregistering of the timeout callback
scanner: Reorder config values
scanner: Fix time unit in log message. Formatting
Merge branch 'feature/scanner_fix_deadlock' into develop

Fixes #476, #483
docs: Update changelog
Merge branch 'develop' of github.com:mopidy/mopidy into develop

Conflicts:
	docs/changelog.rst