Alter Data Model to support the course_navigation placement for LTI tools

This Jira is data model change only - the material in this Jira will be transferred into a new Jira that will cover the actual code.  Once that Jira is created - this Jira will be edited to point to that Jira and much of the content of this Jira will be transferred.

 — To be transferred:

Sakai supports a number of placement types (lessons, editor, migration/import, and assignments).

This Jira will add a checkbox that allows us to indicate whether or not a tool is intended to be used for the course navigation (i.e. left nav) use case. 

It will take a bit of review, design and study to fully define how this will work in Sakai and how it will interact with other features like Site Manage and stealthing.