Simple auto-sanitize mode

Would be nice to add an auto-sanitize mode where it would be enough to say `sanitize=auto` in order to avoid the most harmful clients out there :) Example:

* Ignore `optimize=true` (for update handlers)
* ignore `stream.url`, `stream.body`and `stream.file` params
* limit rows to 200 by default
* limit offset to 2000 by default
* disable `qt` parameter as it can be misused to switch handlers