Handle deletions correctly

[jrjohnson]

For tables which have a soft delete option set their deleted flag to true instead of attempting to remove them from the database.

[jrjohnson]

@saschaben - I found the following list of tables with a deleted column:

+-----------------+
| TABLE_NAME      |
+-----------------+
| course          |
| department      |
| offering        |
| program         |
| program_year    |
| report          |
| report_po_value |
| school          |
| session         |
+-----------------+

A lot of these have relationships and I'm not sure how we want to handle them. I think if we delete a course we should probably walk through and set a deleted flag on all of its sessions, offerings, objectives, etc. Not all of these tables support a soft delete though so we would need to add that to the schema.