Explicitly disallow floats from object settings API

This is to incentivize the transfer from `float` to `double` throughout
the codebase.

src/settings/internal/settings_object_data.h

@@ -59,9 +59,13 @@ private:
         const auto isBool = is_same<bool, Value>::value;
         const auto isInt = is_same<int, Value>::value;
         const auto isDouble = is_same<double, Value>::value;
+        const auto isFloat = is_same<float, Value>::value;
         const auto isString = is_same<std::string, Value>::value
                               || is_same<const char*, Value>::value;
 
+        static_assert( !isFloat,
+                       "'float' is not supported. Use 'double' instead." );
+
         static_assert( isBool || isInt || isDouble || isString,
                        "Type is not supported for the settings object." );
 

src/settings/settings_object.cpp

@@ -65,8 +65,12 @@ std::list<Value> loadListFromDisk( const std::string structName,
     const auto isBool = is_same<bool, Value>::value;
     const auto isInt = is_same<int, Value>::value;
     const auto isDouble = is_same<double, Value>::value;
+    const auto isFloat = is_same<float, Value>::value;
     const auto isString = is_same<std::string, Value>::value;
 
+    static_assert( !isFloat,
+                   "'float' is not supported. Use 'double' instead." );
+
     static_assert( isBool || isInt || isDouble || isString,
                    "Type is not supported for the settings object." );