Added back up and restore options

### Included
Added back up and restore options - Choose from backup only, backup and restore or restore only.
Added number of backup devices option - Choose how many backup devices to split your backup into on disk
Added backup file timestamp options - Set a custom file suffix for the backup device(s), e.g. the current deployment id (or any octopus variable for that matter)

### Not included
In my own usage of this template I've found that changing the BufferCount, BlockSize and MaxTransferSize for the Smo.Backup and Smo.Restore objects increased performance significantly. I also set the Smo.Server.ConnectionContext.StatementTimeout to an explicit value after running into the following unresolved bug in SQL Server 2008: https://connect.microsoft.com/SQLServer/feedback/details/551799/invoke-sqlcmd-querytimeout-0-still-times-out

I haven't included these changes here as they might not apply to all situations.