Replace IS_* with member functions.•••- All user types get an Is* function.
- Only local users are cast using the old function so only local
users get an As* function.
Massive rework of how internal service providers work.•••- ServiceType is dead. All modules use RegisterService now.
- Modules can implement UnregisterService which is called from
DelService now.
- Split the service type prefix into its own field.
- Renamed Service::name to Service::service_name. This revealed
a few bugs.