* Rebase and resolve conflicts from initial patch.
* Reorganise contentitem and contentitem_return pages.
* Add capability checks for contentitem and contentitem_return pages.
* Move the building of Content-Item selection request to a local
  lib function.
* Move contentitem_return processing logic to a local lib function.
* Fix type settings update. Content-item checkbox does not get
  checked/unchecked on load.
* Fix  tool settings update. Disabled content-item checkbox gets unchecked when
  tool settings form is submitted.
* Add "Select content" button on load which launches the content item
  selection dialogue.
* Move hardcoded HTML and JS to mustache templates and AMD modules.
* Use standard YUI dialog for displaying the Content-Item selection page.
* Added processing for the following Content-Item properties:
  - text
  - icon
* On ContentItem selection, fill out form with the configuration data retrieved,
  instead of automatically saving the tool and redirecting to the course page.
* Removed section- and sectionreturn-related code since we're not automatically
  adding the tool on ContentItem selection.
* On mod_lti_mod_form, enable configuration fields if they support ContentItem
  selection.
* New form-field module for setting fields using JS
* Change types_config table's 'value' column from char(255) to text