Write sudo command files in utf8, ebackup utf8 fixes

This branch contains two things:

- Changes in EBox::Sudo to write command files with utf8
- Changes in ebackup to support utf8 in backed up files list and status list 

The EBox::Sudo change has the risk that if some command was already encoded in utf8 individually we could get a double encode. The restore file command in ebackup had this problem. (this is the reason that I had not separated the issue in two branchs)