Toolchain: Small fixes for optionspage

 * Use same icons for add/remove buttons as Qt4 options page does
 * Pop up menu of add button directly

src/plugins/projectexplorer/toolchainoptionspage.ui

@@ -48,6 +48,13 @@
          <property name="text">
           <string>+</string>
          </property>
+         <property name="icon">
+          <iconset resource="../coreplugin/core.qrc">
+           <normaloff>:/core/images/plus.png</normaloff>:/core/images/plus.png</iconset>
+         </property>
+         <property name="popupMode">
+          <enum>QToolButton::InstantPopup</enum>
+         </property>
         </widget>
        </item>
        <item>
@@ -67,6 +74,10 @@
          <property name="text">
           <string>-</string>
          </property>
+         <property name="icon">
+          <iconset resource="../coreplugin/core.qrc">
+           <normaloff>:/core/images/minus.png</normaloff>:/core/images/minus.png</iconset>
+         </property>
         </widget>
        </item>
        <item>
@@ -88,6 +99,8 @@
    </item>
   </layout>
  </widget>
- <resources/>
+ <resources>
+  <include location="../coreplugin/core.qrc"/>
+ </resources>
  <connections/>
 </ui>