Make WikiTextConversions comparisons case-insensitive
- Add tests.
- Use hash-lookup instead of in_array().
- I'm intentionally making all comparisons case-insensitive. If a template or category named "ForbiddenLicense" is forbidden, it never makes sense to allow "forbiddenlicense" then, at least not in the languages strtolower() supports. Note I'm intentionally not using mb_convert_case() because of this.