Doc: List of all Qt overviews which are now termed as explanation

The autogenerated list of overviews was adding the \group command which
included all the groups instead of overviews.
The idea here is to categorize the overviews later on once we have
the list of all overviews.

Task-number: QTBUG-114762
Pick-to: 6.5 6.6
Change-Id: I3cf53886be277abc86b5ec54d399cd6933fbe882
Reviewed-by: Kai Köhne <kai.koehne@qt.io>
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>

src/corelib/doc/src/cbor.qdoc

@@ -6,6 +6,7 @@
     \title CBOR Support in Qt
     \ingroup qt-basic-concepts
     \brief An overview of CBOR support in Qt.
+    \ingroup explanation
 
     \ingroup frameworks-technologies
 

src/corelib/doc/src/ipc.qdoc

@@ -7,6 +7,7 @@
     \ingroup groups
     \ingroup frameworks-technologies
     \keyword ipc
+    \ingroup explanation
 
     \brief An overview of Qt's inter-process communication functionality
 

src/corelib/doc/src/json.qdoc

@@ -6,7 +6,7 @@
     \title JSON Support in Qt
     \ingroup qt-basic-concepts
     \brief An overview of JSON support in Qt.
-
+    \ingroup explanation
     \ingroup frameworks-technologies
 
     \keyword JSON

src/corelib/doc/src/objectmodel/metaobjects.qdoc

@@ -5,7 +5,7 @@
     \page metaobjects.html
     \title The Meta-Object System
     \brief An overview of Qt's meta-object system and introspection capabilities.
-
+    \ingroup explanation
     \ingroup qt-basic-concepts
     \keyword meta-object
     \keyword Meta-Object System

src/corelib/doc/src/objectmodel/properties.qdoc

@@ -5,7 +5,7 @@
     \page properties.html
     \title The Property System
     \brief An overview of Qt's property system.
-
+    \ingroup explanation
     \ingroup qt-basic-concepts
     \keyword Qt's Property System
 

src/corelib/doc/src/objectmodel/signalsandslots.qdoc

@@ -8,6 +8,7 @@
     \ingroup qt-basic-concepts
     \brief An overview of Qt's signals and slots inter-object
     communication mechanism.
+    \ingroup explanation
 
     Signals and slots are used for communication between objects. The
     signals and slots mechanism is a central feature of Qt and

src/dbus/doc/src/qtdbus-overview.qdoc

@@ -5,6 +5,7 @@
     \page qtdbus-overview.html
     \title Qt D-Bus Overview
     \brief Provides insight into the Qt Qt D-Bus module.
+    \ingroup explanation
 
     D-Bus is an Inter-Process Communication (IPC) and Remote Procedure
     Calling (RPC) mechanism originally developed for Linux to replace

src/gui/doc/src/richtext.qdoc

@@ -11,7 +11,7 @@
     \page richtext.html
     \title Rich Text Processing
     \brief An overview of Qt's rich text processing, editing and display features.
-
+    \ingroup explanation
     \ingroup frameworks-technologies
     \ingroup qt-basic-concepts
     \ingroup best-practices

src/xml/doc/src/xml-processing.qdoc

@@ -15,6 +15,7 @@
 /*!
     \page xml-processing.html
     \title XML Processing
+    \ingroup explanation
 
     \brief An Overview of the XML processing facilities in Qt.