Issue: Custom settings problems in domain manager

When changing some URL settings via the domain manager, this makes it very difficult to create correct .htaccess configurations, and it can make articles completely unavailable when the admincp on one domain is used to rebuild namespaces over another. Namespace "functions" can also be broken if changed on a domain basis.

The only way to fix this is to forbid the URL-related settings from changing on a domain basis. Similar effects can be achieved now using custom relative paths via the namespace manager.

Fixed for the next build.