Exclude a student's assignment from grading

User Interface Changes

API Changes

Looks like this is similar to the Drop Lowest Grade. They all seem to follow the same pattern that we have to make changes to a data model object all the way up to the db to store this flag in a sensible place, then make changes to the calculations themselves, which seem to all be in the GradebookManagerHibernateImpl Class.

The nice thing for this change is that I think all we need to do is modify the hibernate queries to exclude items with this new flag (e.g. "IS_EXCLUDED=Y" or something along those lines).

Here are the methods that look like they're going to have to be touched:

1. getTotalPointsEarnedInternal() – both signatures
2. getTotalPointsInternal() – both signatures
3. getLiteralTotalPointsInternal() – both signatures