Deskew configuration file's px_to_scan_ratio parameter is redundant with scale metadata

[talonchandler]

When we developed deskew we were not passing scale metadata correctly, so we needed to pass px_to_scan_ratio to the routine. Now we are passing scale metadata, so px_to_scan_ratio can be omitted from the deskew configuration file.

• I am only suggesting that we drop px_to_scan_ratio from the CLI interface...the lower level interfaces should keep this parameter
• This requires datasets to have correct scale metadata, but we can modify old or incorrect datasets with mantis update-scale-metadata
• This is not a severe problem, but it did cause me some confusion as I was debugging my PSF figures. I (incorrectly) thought I could copy the px_to_scan_ratio from a working deskew parameter file, but actually I needed to calculate this from the input data scales.