Scaling in percent manually

At the moment PM only supports automatic scaling, which is working fine. But many customers want's to set scaling via percentages manually.

Because of this missing function, the operator is forced to use e.g. Fiery CommandWorkstation to set the scaling manually (as far as there's Fiery Controller). This means, you have to use two different frontends. Much better would be to be able to stay in their TotalFlow environment, without being forced using efi tools additionally.