updates data_isis to return positions in the correct frame (#214)

* Added helper func to convert ISIS table to rotations

* Added ISIS frame chain

* Fixed rotation direction in data_isis

* First pass at data_isis sun position

* added sensor position to data_isis

* More updates

* Updated data_isis test after removing label

* Updated data_isis to new frame chain

* updated to get tests passing

* Cleaned up how ISIS tables are read

* Fixed missing return

* Cleaned up fixtures in test_transformation

* Added km to m conversion