Implement a dialog to plot and export GPS data

Create a dialog with buttons to plot and export GPS data.

Show information about a GPS data point when user clicks on it.

#19 (closed)

sohstationviewer/model/gps_point.py

+from typing import NamedTuple
+
+
+class GPSPoint(NamedTuple):
+    last_timemark: str
+    fix_type: str
+    num_satellite_used: int
+    latitude: float
+    longitude: float
+    height: float