[TD] sanitize Scale preferences

- take care that custom scale is only in effect if the scale type is 'Custom'
- use UnitSpinBox for Template Mark
- use uniform width for all scale edits
- also use UnitSpinBox for Balloon Kink

src/Mod/TechDraw/Gui/DlgPrefsTechDraw2Imp.cpp

@@ -34,8 +34,10 @@ DlgPrefsTechDraw2Imp::DlgPrefsTechDraw2Imp( QWidget* parent )
   : PreferencePage( parent )
 {
     this->setupUi(this);
-//    pdsbTemplateMark->setUnit(Base::Unit::Length);
 
+    this->pdsbTemplateMark->setUnit(Base::Unit::Length);
+    connect(this->cbViewScaleType, SIGNAL(currentIndexChanged(int)),
+        this, SLOT(onScaleTypeChanged(int)));
 }
 
 DlgPrefsTechDraw2Imp::~DlgPrefsTechDraw2Imp()
@@ -43,6 +45,16 @@ DlgPrefsTechDraw2Imp::~DlgPrefsTechDraw2Imp()
     // no need to delete child widgets, Qt does it all for us
 }
 
+void DlgPrefsTechDraw2Imp::onScaleTypeChanged(int index)
+{
+    // disable custom scale if the scale type is not custom
+
+    if (index == 2) // if custom
+        this->pdsbViewScale->setEnabled(true);
+    else
+        this->pdsbViewScale->setEnabled(false);
+}
+
 void DlgPrefsTechDraw2Imp::saveSettings()
 {
     pdsbToleranceScale->onSave();