fphammerle/freesurfer-surface: descriptive exceptions

Removed

• compatibility with python3.5

• added default value for creator to fix TypeError in write_triangular when unset
• write_triangular: raise descriptive ValueError when missing volume_geometry_info (instead of TypeError)
• find_label_border_polygonal_chains: raise descriptive RuntimeError when annotation was not loaded (instead of TypeError)

• fixed type hints