first pass at script for fixing ddr-densho-255
break the working code into subfunctions
mark --entityid as required arg

ddrdensho255fix is specific to this collection, in which entities
may have thousands of files, so we're only doing one entity at
a time.
Merge branch '149-elasticsearch-docstore' of https://github.com/densho/ddr-cmdln into 149-elasticsearch-docstore