bounce: refactored. a lot.

best not to look at the diff, and instead just look at the plugin before and after. New version has functions with names that describe what they test.

Each check can be enabled/disabled in bounce.ini section [checks]

Rejection can be enabled/disabled for each check in bounce.ini [reject]

Config refreshing is done by refresh_config, once per connection.

Extending with future checks is straight forward.

Tests are included.