Add --catscan mode to skip rendering and only build output catalog
Don't calculate bounds in catscan mode so that sn-cut = 0 can be used
Fix factor of 2 bug in component sizes
Change default q from 0 to 1 when component is not present
Add f_b and z to catalog output
Implement new psf cmd-line parameters
Change pixel S/N cut default from 0.1 to 0.5 to match the paper
Rework top-level flow control. Remove --catscan and add --save-field option.
Add flux SNR calculation and save in output catalog