Added SFTP support in wotaskd, in preparation of a Jenkins plugin

The SFTP server will run on port 6022. Only password authentication will work, you need to provide the password of your wotaskd installation.
Adding shell support so that we can do things like symbolic links
Merge branch 'integration' into wotaskd_ftp
Adding the TCP port number for wotaskds built-in SSH server as a property
Allowing empty passwords is a bad idea. If you wish to use the built-in SSH server, set a password for wotaskd
Merge branch 'integration' into wotaskd_ftp
Merge branch 'integration' into wotaskd_ftp
Adding a property to enable/disable the built-in SSH server
SSH server in wotaskd is now disabled by default
Merge pull request #395 from pascalrobert/wotaskd_ftp

Built-in SSH server in wotaskd (take 2)