Filter out expected SQL errors

Filter out expected SQL errors on duplicate entries
Change filter of expected SQL errors

Filter out "SQLSTATE Class code 23: Constraint Violation" because of
expected duplicate entries.
Consider adding a Minz_Log::DEBUG level
Merge branch 'sqlDuplicateEntries' of https://github.com/Alkarex/FreshRSS into Alkarex-sqlDuplicateEntries