Simplify settings down to just Metric / ShowOtherUnit.

Factor out some common code.

public_html/config.js

@@ -7,13 +7,13 @@
 
 // -- Output Settings -------------------------------------
 // Show metric values
-// This controls the units used in the plane table,
-// You can choose to enable Metric or Imperial or both.
-// If you enable both, by setting PreferMetric to either true or false,
-// you control which unit is displayed first.
-PreferMetric = true;
-EnableMetric = true;
-EnableImperial = false;
+// The Metric setting controls whether metric (m, km, km/h) or
+// imperial (ft, NM, knots) units are used in the plane table
+// and in the detailed plane info. If ShowOtherUnits is true,
+// then the other unit will also be shown in the detailed plane
+// info.
+Metric = false;
+ShowOtherUnits = true;
 
 // -- Map settings ----------------------------------------
 // These settings are overridden by any position information