Update docblocks
FIX: Use Injector API for managing Member_Validator instance.

Updates the CMS profile page and SecurityAdmin to give developers a few ways to customise the required fields.

Added extension hook updateValidator for getValidator for things like modules to inject required fields to go along with Injector for replacing the entire class for project specific use.
Merge pull request #2537 from wilr/membervalidator

FIX: Use Injector API for managing Member_Validator instance.