corrected input velocity units to vel3d-cd functions [DPS still incorrect]
added unit tests for up velocities of vel3d-bcd and velpt
updated documentation in ion_functions\data\README.TXT
updated DPA function documentation.
reordered functions within vel_functions.py and added table of contents
@s-pearce Ready for review and merge.
@cwingard Ready for review and merge.
corrected input velocity units to vel3d-cd functions [DPS still incorrect] added unit tests for up velocities of vel3d-bcd and velpt updated documentation in ion_functions\data\README.TXT updated DPA function documentation. reordered functions within vel_functions.py and added table of contents
@s-pearce Ready for review and merge. @cwingard Ready for review and merge.