updated path with special functions to flag plates and zero pad fieldIDs for relevant run2d version

[Sean-Morrison]

updated path with special functions to flag plates and zero pad fieldIDs for relevant run2d version

[havok2063]

I think this looks ok to me. I suggested some code changes that better conform to python style guides, and improve readability. I also have some questions about the pad_fieldid function, but I'll add those to the tree PR.

Can you add some tests for these, and make sure all the tests pass? You can probably just add your examples to the test_special_function test in tests/paths/test_sdss5.py. This is a test that checks that special functions used in paths return the proper content.

sdss_access/tests/path/test_sdss5.py

Line 51 in 09c5d58

def test_special_function(self, path, name, special, keys, exp):

If you're not familiar with writing tests for python, I can help. Just ping me.