Add new valid BridgeDistribution methods

This adds settings, telegram and reserved as valid BridgeDistribution methods.

This change prevents the warning "Unrecognized BridgeDistribution value X. I'll assume you know what you are doing..." from being logged, which is potentially confusing to bridge operators who set the values using this option.

Note that I have added reserved which is valid (and tested), but is not new. Please let me know if this was intentionally excluded and I will remove it again.