Some cleanup to ProtectionForm:

Some cleanup to ProtectionForm:
* When the user doesn't have permission to protect/unprotect the page, display a page with the title set to "View protection level for ...", then the permissions errors and the current protection levels. Except for the title, this was already the case for permissions errors, but when the database was read-only this was throwing an exception due to the change in OutputPage::readOnlyPage()
* Moved check for NS_MEDIAWIKI a level up, so that is it also catched on page save, and make the output in such case much more user friendly
* Changed edit token to be salted with array( 'protect', 'page name' ) (as for action=watch)
* Allow extensions to return false in ProtectionForm::save hook for consistency with other hooks and in that case fill the error message with 'hookaborted' if the extension does not provide an customised error message.
* Changed ProtectionForm::show() to accept an array of message name and its parameters in addition of a string with raw HTML and converted calls to use the new method. This also means that ProtectionForm::save can use this
* Removed the setSubtitle() call for the 'formerror' message in case of error since it's overriden by the "back link"