Uses non-existant source options for some scanners.

[Gotisch]

I have a Brother ADS-1100W. Scanning fails. Error as follows.

ERROR: Could not run command scanadf -d "brother4:net1;dev0" --source "ADF Duplex" --mode Color --resolution 300dpi --y-resolution 300dpi -o /tmp/20160720_020004/page_%04d -y 876 --page-height 376

The ADS-1100W only supports the following colour mode and source options:

--mode Black & White|Gray[Error Diffusion]|True Gray|24bit Color[Fast] [24bit Color[Fast]] --source Automatic Document Feeder(left aligned)|Automatic Document Feeder(left aligned,Duplex)|Automatic Document Feeder(centrally aligned)|Automatic Document Feeder(centrally aligned,Duplex) [Automatic Document Feeder(left aligned)]