Doc: move Class View plugin docs to .cpp files.

QDoc does not find docs in the .h files.
Use \brief only for namespaces, classes, enums, and properties.
Use standard wording for \brief and \fn.
Use \a and \c according to guidelines.

Fix grammar and style.

Change-Id: Ib685a03c97ef38661ecc156f61d70085514357fc
Reviewed-by: Erik Verbruggen <erik.verbruggen@digia.com>

src/plugins/classview/classviewtreeitemmodel.cpp

@@ -40,8 +40,9 @@ namespace Internal {
 ///////////////////////////////// TreeItemModelPrivate //////////////////////////////////
 
 /*!
-   \struct TreeItemModelPrivate
-   \brief Private class data for \a TreeItemModel
+   \class TreeItemModelPrivate
+   \brief The TreeItemModelPrivate class contains private class data for
+   the TreeItemModel class.
    \sa TreeItemModel
  */
 class TreeItemModelPrivate
@@ -53,6 +54,11 @@ public:
 
 ///////////////////////////////// TreeItemModel //////////////////////////////////
 
+/*!
+   \class TreeItemModel
+   \brief The TreeItemModel class provides a model for the Class View tree.
+*/
+
 TreeItemModel::TreeItemModel(QObject *parent)
     : QStandardItemModel(parent),
     d(new TreeItemModelPrivate())
@@ -118,6 +124,10 @@ void TreeItemModel::fetchMore(const QModelIndex &parent)
     return Manager::instance()->fetchMore(itemFromIndex(parent));
 }
 
+/*!
+   Moves the root item to the \a target item.
+*/
+
 void TreeItemModel::moveRootToTarget(const QStandardItem *target)
 {
     emit layoutAboutToBeChanged();