Fix database upgrader to work properly with PDO.
Insertion of batch spots where safe() was called did not work properly because even though we cast to int, is_int() returns false but is_double() returns true.
Upgrade database schema version so we can delete older spots, fixes GH issue #1888
Migrate all batchInsert() code to also use seperate parameter and query texts to make sure all data is in the correct format.
Simplify the way we handle Message-ID's in the code, we now remove them from the getOverview() call so all other code can just ignore them.
Remove arrayValToInOffset() code as it is not needed anymore
Increase size of ring buffer
Strip <>'s from Reference header in the XOVER call as well
Fix parameter escaping in advanced search filter. Fixes GH issue #1889