Add way to bulk import dblog page_not_found errors as Redirect_404 entries

Problem/Motivation

When the Redirect404 module is installed it misses the history of records available through the database logging / dblog / watchdog system.

Proposed resolution

Add a way to bulk import database logging 404 errors as Redirect 404 entries, e.g. a Drush command.

Remaining tasks

Build the functionality.

User interface changes

TBD

API changes

TBD

Data model changes

n/a