Improve documentation for UI classes

src/qt/transactionview.h

@@ -16,6 +16,9 @@ class QFrame;
 class QDateTimeEdit;
 QT_END_NAMESPACE
 
+/** Widget showing the transaction list for a wallet, including a filter row.
+    Using the filter row, the user can view or export a subset of the transactions.
+  */
 class TransactionView : public QWidget
 {
     Q_OBJECT