Misc updates to gatePolygon()
Misc updates to gatePolygon()

Switched gate edges to use 1st / 99th percentiles, rather than min/max (was causing annoying issues for random highly negative values)

Added help text and renamed input 'position' to 'polygon'

jonesr18/MATLAB_Flow_Analysis,jonesr18/MATLAB_Flow_Analysis,jonesr18/MATLAB_Flow_Analysis,jonesr18/MATLAB_Flow_Analysis