Refactor include_columns and exclude_columns
remove n_data_cols
Make more use of colnames property
initial test and validations of array-ifyable coordinates
More testing
more complete tests
activate distance/angle shape matching
fix repr/str for array coordinates
Complete changes to make galactic and fk5 transforms pass
Test enhancements incl. distances and fk4
Make FK4 conversions array-compatible and fix distance units
Added example of angle usage to coordinates documentation
Fix repr for array distances
Test precision with array coordinates
Add FK4 value test
Add test for string arrays
fix for typo in coordinates __repr__
check (and fix) reverse-fk4 transform

array support should now be in for all transforms, so this closes #884
e-terms now use `asarray` instead of `array`, as suggested by @mdboom
Add explicit exeption if equinox is not a scalar as suggested by @astrofrog