Base: make UnitsApi::toString method of Quantity

This static method takes Quantity as a parameter, so make it
method of Quantity directly.

src/Base/Quantity.cpp

@@ -241,6 +241,11 @@ Quantity Quantity::operator-() const
     return Quantity(-(this->myValue), this->myUnit);
 }
 
+std::string Quantity::toString(const QuantityFormat& format) const
+{
+    return fmt::format("'{} {}'", UnitsApi::toNumber(myValue, format), myUnit.getString());
+}
+
 std::string Quantity::getUserString() const
 {
     double dummy1 {};  // to satisfy GCC

src/Base/Quantity.h

@@ -157,6 +157,9 @@ public:
         myFormat = fmt;
     }
 
+    std::string
+    toString(const QuantityFormat& format = QuantityFormat(QuantityFormat::Default)) const;
+
     std::string getUserString() const;
     /// transfer to user preferred unit/potence
     std::string getUserString(double& factor, std::string& unitString) const;

src/Base/UnitsApi.cpp

@@ -27,7 +27,6 @@
 #endif
 
 #include <CXX/WrapPython.h>
-#include <fmt/format.h>
 
 #include "Exception.h"
 #include "UnitsApi.h"
@@ -94,11 +93,6 @@ void UnitsApi::setSchema(const size_t num)
     schemas->select(num);
 }
 
-std::string UnitsApi::toString(const Quantity& quantity, const QuantityFormat& format)
-{
-    return fmt::format("'{} {}'", toNumber(quantity, format), quantity.getUnit().getString());
-}
-
 std::string UnitsApi::toNumber(const Quantity& quantity, const QuantityFormat& format)
 {
     return toNumber(quantity.getValue(), format);

src/Base/UnitsApi.h

@@ -52,17 +52,11 @@ public:
     static std::string schemaTranslate(const Quantity& quant);
 
     /**
-     * toString & toNumber:
      * Quantity to string. Optionally apply format
      * The string is a number in C locale (i.e. the decimal separator is always a dot)
      * Scientific notation (if needed).
      */
 
-    /** INCLUDES unit */
-    static std::string
-    toString(const Quantity& quantity,
-             const QuantityFormat& format = QuantityFormat(QuantityFormat::Default));
-
     /** Does NOT include unit */
     static std::string
     toNumber(const Quantity& quantity,

src/Gui/propertyeditor/PropertyItem.cpp

@@ -1187,7 +1187,7 @@ void PropertyUnitItem::setValue(const QVariant& value)
     if (!hasExpression() && value.canConvert<Base::Quantity>()) {
         const Base::Quantity& val = value.value<Base::Quantity>();
         Base::QuantityFormat format(Base::QuantityFormat::Default, highPrec);
-        setPropertyValue(Base::UnitsApi::toString(val, format));
+        setPropertyValue(val.toString(format));
     }
 }