Administration page for question types

We need an administration page for question types, like admin/modules.php, admin/blocks.php or admin/filter.php. This is MDL-6751.

Requirements

See which question types are installed, and which version each one is.

See how many instances of each type there are and get a list of those instances and which context they belong to.

Provide a way for the administrator to control which question types can be created. (It may be necessary to leave a question type installed, so that old quiz results can be reviewed, but the administrator may wish to prevent the creation of new questions of that type, so it can be phased out.)

If there are no questions of a particular type in the database, provide a delete option.

Allow each question types to have its own settings page.

(Technical) move qtype_xxx_version config variables to the config_plugins table.

Design

The main "Manage question types" page page will use a table like the other Manage XXX pages. The table will have columns "Question type", "No. questions", "Version", "Available?", "Delete", "Settings".

The number in the "No. questions" column will be a link to a report that lists all the question categories that contain questions of this type. It will be a table with columns "Context", "Question category", "Questions" and "Hidden questions". The context will be a link to that context, if the user has access. The question category will be a link to the question bank screen for that category.

The "Available?" column