Sync does "pull --ff" in branch
Refactor SyncTask
Log to .vb/.var/app.log
Get rid of global _logger variable
Rename: BaseTask.exit -> fail
Fix log level

"logger.setLevel(logging.NOTSET)" was wrong because then the level
of the root logger is used
Log STDOUT and hide it from the normal output
Add show_failed_stdout option to `Launchable.call`
Make command in log message more readable
Improve log message
Fix log message
Refactor Launchable
Tweak SyncTask
Add --force to sync command
Tweak log messages