Add backlog of errata

[Tembrel]

There's a long backlog of reported errata that has not been incorporated into the errata page. Some of them are undoubtedly repeats, but many are not.

[Tembrel]

Issue #16 doesn't add backlog, but does annotate a large percentage of errata that were addressed in 6th printing. Some of the backlog undoubtedly belongs to this category.