deployment.php: prints exception with complete stack trace with options --debug
deployment.php: options `purge, before, after` are split by lines (BC break)
FtpServer: improved purge(), renames directories before they are purged [Closes #40]
refactoring
Deployment: more robust checking for errors in before and after jobs
Deployment: before and after jobs can be system commands (in before jobs, commands are executed before URLs) [Closes #41]