Handle orphaned documents when a taxed AP/AR Open Item is cancelled

Handle orphaned documents when a taxed AP/AR Open Item is cancelled.  Clear database entry.
There's no reason to ever merge into master locally. Branch directly from `4_6_x`, or whichever branch you intend to eventually submit a PR against, e.g. `handle-orphaned-documents`, and always pull other branches into `handle-orphaned-documents` whenever there are updates you want to merge in, and do all your work on `handle-orphaned-documents` or whatever your incident is.