Item Types and Item Display Types

## Overview

What to do to add new item types or item display types:

- add new table to assessment-item-types-create.sql
- add entry to matrix table item_type -> display_type in assessment-types-create.sql
- add content type data to tcl/as-install-procs.tcl. adhere to the naming standards!!
- add tcl procs to tcl/as-item-type-$$-procs or tcl/as-item-display-$$-procs with ::new, ::edit, ::copy procs. adhere to naming standards!!
- add admin pages to add new instance: www/admin/item-add-$$ or www/admin/item-add-display-$$
- add admin pages to edit new instance: www/admin/item-edit-$$ or www/admin/item-edit-display-$$
- add pages to display data: lib/item-show-$$ or lib/item-show-display-$$