Spun off from https://jira.ez.no/browse/EZP-25946 / https://github.com/ezsystems/ezpublish-kernel/pull/1825

• Doc: It doesn't throw InvalidArgumentException on existing entry, it updates it instead.
• Doc: It doesn't throw BadStateException on zero rowcount anymore, as that is unreliable across DBMSs.
• Removed 'expired' from update statement, as that value isn't provided in the insert statement.
• Removed rowcount check (see above).
• Use DateTime instead of timestamp in the test, as the BinaryFileCreateStruct->mtime docblock says.
• Convert DateTime to timestamp before insert query, but also allow timestamp since some code has been using that (see above).