Added support for FTP and SFTP.
Modified definition of user variables into 3 blocks - (S)FTP settings, Email settings, Backup settings (therefore it seems a lot of changes, but many of those are just moved lines from one place to another).
Modified email sending logic - email may be sent even if it does not contain backup.
Modified upgrade go/no-go logic - now upgrade is performed if at least one of the backup storages succeeds (i.e. backup is sent at least to one of (s)ftp or email).
Added option to upload backups via FTP.
Modified some part of the code (mainly Send email section and Cleanup section) to reflect on new conditions as when cleanup may be performed (it is not perfect though).
Current development version is rc4, but it's not recognized by the script, however I'm not sure what would be the version number on final release and It might see rc version as the newer one.
