SuperDARN Radar Software Toolkit (RST) 4.1

This patch release features the updated AACGM 2.6 that was released by Dr. Simon Shepherd at Dartmouth College (http://superdarn.thayer.dartmouth.edu/aacgm.html). The RST is actively developed and maintained by the SuperDARN Data Analysis Working Group (https://homepage.usask.ca/~pbp672/DAWG.html).