Entity Name Validation scope should be shared and global

Currently, each (sub)wiki has its own name strategy configuration.
This has two negative consequences:
1. The configurations can be inconsistent, with subwikis having over-permissive configurations leading to document name incompatible with the server's restrictions.
2. The configuration cache is overriden by the latest edited configuration, so if a subwiki edit its configuration, it becomes global for all the wikis.

Proposition:
These two points can be solved by only proposing a single global configuration on the main wiki, and no in the sub-wikis.