Identify test data

[wmwv]

1. What minimal data do we want for unit tests.
2. What minimal data do we want for a test run.
3. What is the first test we would run at DCC or NERSC or another place that has a set of data.

[wmwv]

1. Will create photometry_test_data repo.
2. Put in images and catalogs as needed as test arrive.
3. Add as submodule
4. Write tests against