Fix numerous bugs in view/change file attributes dialog

[ssvine]

Fix bugs and add some improvements.

Bugs:

• file mode is shown incorrectly
• file mode cannot be correctly changed
• owner and group cannot be changed
• cannot set user and group in SFTP mode (SFTP protocol v3, e.g. openssh)
• owner and group drop down list contains repeated items
• FTP change attributes assertion
• add X to directories + recursive checkboxes misbehaviour
• ok button misbehaviour
• recursive checkbox is invisible when file is symlink
• adding object into sorted TStringsList is broken

Improvements:

• enrich owner and group combo boxes with any possible names
• add logged on user to a users list for owner combo box
• add numeric textboxes for changing uid and gid for servers that can only use numeric values

[michaellukashov]

Thanks, added