Issue #2783075 by phenaproxima, claudiu.cristea, ohthehugemanatee, chx, mikeryan: Add a "download" process plugin, remove remote capability from FileCopy

Issue #2706405 by heddn, edysmp, davidparedes21, mikeryan, phenaproxima: File migrations *always* copy in files, even if the files were off-line copied to destination

Issue #2695297 by mikeryan, ohthehugemanatee, quietone, vasi, Sharique, chx, benjy, phenaproxima, heddn, benjifisher: Refactor EntityFile and use process plugins instead