STYLE: Rename icon filename {minus, plus}-16.png into {minus, plus}.png

Libs/Widgets/Resources/CTKWidgets.qrc

@@ -1,8 +1,8 @@
 <!DOCTYPE RCC><RCC version="1.0">
   <qresource>
     <file>Icons/edit.png</file>
-    <file>Icons/minus-16.png</file>
-    <file>Icons/plus-16.png</file>
+    <file>Icons/minus.png</file>
+    <file>Icons/plus.png</file>
     <file>Icons/expand-down.png</file>
     <file>Icons/expand-up.png</file>
   </qresource>

Libs/Widgets/Resources/UI/ctkAddRemoveComboBox.ui

@@ -40,7 +40,7 @@
      </property>
      <property name="icon">
       <iconset resource="../CTKWidgets.qrc">
-       <normaloff>:/Icons/plus-16.png</normaloff>:/Icons/plus-16.png</iconset>
+       <normaloff>:/Icons/plus.png</normaloff>:/Icons/plus.png</iconset>
      </property>
      <property name="iconSize">
       <size>
@@ -63,7 +63,7 @@
      </property>
      <property name="icon">
       <iconset resource="../CTKWidgets.qrc">
-       <normaloff>:/Icons/minus-16.png</normaloff>:/Icons/minus-16.png</iconset>
+       <normaloff>:/Icons/minus.png</normaloff>:/Icons/minus.png</iconset>
      </property>
      <property name="iconSize">
       <size>