Work on import/export.
Set EFFECTIVE-DATE when reading.
Put collection bookkeeping bits back into xdb.
Use keys when importing.
Save newly imported docs.
Fix merging artefacts.
Add compare-docs function.
Remove duplicate definitions.
Don't move objects created as forward-references into old-versions.
Issue a warning for collection mismatch between different versions of an object.
More compact collection mismatch warning.
Move persist from xpacks.
Remove :load-from-file-p option from add-collection.
Its misuse can lead to data corruption.
Add clear-old-versions.
Change clear-old-versions arglist.
Add tests.
Fix storable-object initialization.
Add the ability to change between storable-class and storable-versioned-class.