Improving streographic triangle functionality #52
Description
Our current streographic_triangle_implementation was designed to work with an older pyxem architecture. To update it I propose the following.
Create a function get_beam_direction_streographic(density,crystal_system)
which more or less replicates (with bugfixes) the existing functionality.
Add a second function, get_rotation_list_streographic(density,beam_resolution,crystal_system) that behaves in a manner that is consistent with other rotation_list generators.