- Added implementation for external command "xtrapbookback". - Refactored all the journal "bookback" commands to a shared implementation (since they all do the same thing).
- Added implementation for external command "xtrapbookback".
- Refactored all the journal "bookback" commands to a shared implementation (since they all do the same thing).

jfroy/rivenx,jfroy/rivenx,jfroy/rivenx,jfroy/rivenx