Currently KConfgiSkeleton cannot manage item entry in subgroup, like
```
[General][Colors]
MyItem=foo
```
Example of use
```
// Generated Class with KConfig compiler, inherits KConfigSkeleton
KConfigGroup generalGroup( &config, "General" );
KConfigGroup colorsGroup = config.group( "Colors" )
myItem->addGroup(cg); // Now can take a KConfigGroup
addItem(myItem, "MyItem");
```