Add Distance to Table Info

Add distance to table if site coordinates are provided and sort the
table by distance.  If coordinates aren't provided, the column isn't
displayed.
Center "Distance from Site" for Selected Plane

Center "Distance from Site" under "Lat/Long" for selected plane.
Add Degree Symbol to Track Value

Add the degree symbol to the "Track:" value in the plane details
section.
Change the Background Color for a Plotted Plane

Changed the background color for a plotted plane in the planes table to
something that was more easily visible.
Fix W3C Validation Errors

Fixed some W3C validation errors.
Merge remote-tracking branch 'origin/fix_w3c_validation'
Merge remote-tracking branch 'origin/change_plotted_plane_table_bg_color'
Merge remote-tracking branch 'origin/center_selected_plane_distance'
Merge remote-tracking branch 'origin/add_distance_to_table'