Polish the settings dialog.

Add a title label to the pages. Use QGroupBoxes throughout.
Extend SavedAction to work with checkable QGroupBoxes. Polish UI files,
use common layout for VCS plugins. Performance: Apply only visited
settings pages. Add search keywords.

Task-number: QTCREATOR-26

src/plugins/cpptools/cppfilesettingspage.ui

@@ -6,7 +6,7 @@
    <rect>
     <x>0</x>
     <y>0</y>
-    <width>424</width>
+    <width>441</width>
     <height>503</height>
    </rect>
   </property>
@@ -19,9 +19,6 @@
        <verstretch>0</verstretch>
       </sizepolicy>
      </property>
-     <property name="title">
-      <string>File Naming Conventions</string>
-     </property>
      <layout class="QFormLayout" name="formLayout">
       <property name="fieldGrowthPolicy">
        <enum>QFormLayout::ExpandingFieldsGrow</enum>
@@ -61,7 +58,7 @@
        </widget>
       </item>
       <item row="3" column="1">
-       <widget class="Utils::PathChooser" name="licenseTemplatePathChooser" native="true"/>
+       <widget class="Utils::PathChooser" name="licenseTemplatePathChooser"/>
       </item>
      </layout>
     </widget>