refactored decals_sim so that a single chunk or many chunks can be run, an any case the user provides a seed which determines the seeds for all chunks 0 to 999
refactored decals_sim so that a single chunk or many chunks can be run, an any case the user provides a seed which determines the seeds for all chunks 0 to 999

legacysurvey/legacypipe,legacysurvey/legacypipe