PP save default gridded polar axis.
Merge pull request #546 from bjlittle/pp_cs_save

PP save default gridded polar axis.
Merge pull request #552 from esc24/traj_test_data

Switched from sample data to test data.
NAME fileformat support.
Refactor to move more into name_loaders.py
Docstrings.
Modified priorities in custom loader example to prevent use of new built
in NAME loader.
Updated known_loaders.txt
Review actions.
Simplified header loading.
Review actions.