Forbid having _revision_expired < _revision_added in _revision tables

[strk]

The function ver_get_$schema$_$table$_revision(p_revision integer) (and possibly other) assume that _revision_expired is always bigger or equal to _revision_added failing which no revision would ever be considered to contain the corresponding record of a table.

For this reason it would make sense to enforce such condition as an integrity constraint (a check).

Such database corruption was spotted and reported by downstream project here: https://github.com/linz/ds-dev-team/issues/46

[palmerj]

Would be good to understand the performance hit of such a constraint

[strk]

It could be now a good occasion to test that performance hit, do you want a PR for this @imincik for testing as part of your current performance analisys ?

[strk]

PR #121 is ready for review/test

[stale]

This issue has been automatically marked as stale as there has not been any activity for sometime. The issue will be closed in 14 days if no further activity.

[imincik]

Still relevant.