Mapping Afr stopovers and visualizing autumn stops

Added a new script to tidy and use the most recently downloaded Movebank
data from Sep 2014 and add LOS and season for mapping African stopovers in
ArcGIS. Added some new code to visualize autumn stopover data using
ggplot. Added models comparing outputs for short vs long stopovers, and
wrote a new source script to calculate stopover duration data for any
data.