Because generally using QString.arg() results in an error for
strings without %1
Also use the static database() function instead of creating
a temporary instance during close.
Extend B64_BLOB from "VARCHAR(8000)" which was a good
common value - until I realized that CRL may become pretty large.
Use "TEXT" for all databases but MariaDB, where LONGTEXT is used.
Add database type check via SQL query to detect the
correct database even behind an ODBC Driver.
