BNS Upgrade: managed namespace improvements

[larry]

@hank

This proposal would make this type of functionality more explicit, without the need for extra steps to modify a price function. Instead the new BNS contract would include new functionality:

+1 to making this functionality more specific.

@hank

Namespace manager functions:

It might be useful to have granular settings for this. Example: Some namespaces might gate registrations but commit to never burning or transfer names.