Issue #2845488 by Jo Fitzgerald, gerzenstl, Pavan B S, Yogesh Pawar, gaurav.kapoor, quietone, phenaproxima, mikeryan: Add documentation to SkipOnEmpty process plugin

Issue #2682461 by arunkumark, jonhattan, quietone, benjy, xjm, RavindraSingh, catch: Add links to documentation in all migrate process plugins

Issue #2665992 by alexpott, klausi, heykarthikwithu, xjm, tstoeckler: @file is not required for classes, interfaces and traits

Issue #1392754 by tss, justAChris, jhodgdon: Comply with new documentation standards for @file for namespaced class files

Issue #2509496 by chx, benjy, phenaproxima: Make migrate process plugins more flexible/less boilerplate