Loading POI files

I believe there is an error in the code related to load POI files. The code will only read the first line of any POI file and return. There is no `while ((lineOfText = file.ReadLine()) != null)` pseudo code. If you have a file with multiple POIs, only the first one will be read and displayed. The `public static void POILoad()` method needs to be updated in the MissionPlanner/Utilities/POI.cs file to reflect this change.

Open MissionPlanner/Utilities/POI.cs and inspect the public static void POILoad() method, focusing on how it reads lines from the POI file. Verify the behavior with a file containing multiple POIs; done means every POI is loaded and displayed rather than only the first line.

Written by the indexing model from the issue text.