clean_up() method breaks on SOURCES table

[hover2pi]

Figure out how to run clean_up() on the SOURCES table. The only required column is id, which inherently won't be identical so what are we looking for in conflicted records?

The choices I see are:

1. Don't run clean_up() on such tables, or
2. Require at least one column other than id to be NOT NULL

[dr-rodriguez]

I would argue that at least the designation or shortname column should not be null.
We may also consider identifying duplicates by matching by RA/Dec within some radius.

[hover2pi]

Ok, we can do that. So in general we'll just make sure every table has a NOT NULL id column and one other.

Make sure NOT to just check the NOT NULL box in the SQLite Browser because db.clean_up() will then kick out all the records that fail this constraint. We have to first go in and make sure all records have something in that column.