[skip-ci][docs] Rename top-level groups for uniformity

Also put TreePlayer library under TTree and REve under Graphics

Author: silverweed

geom/geom/doc/index.md

@@ -1,4 +1,4 @@
-\defgroup Geometry The Geometry Package
+\defgroup Geometry Geometry
 
 
 The %ROOT geometry package is a tool for building, browsing,

graf3d/eve7/src/REveTypes.cxx

@@ -17,7 +17,8 @@ using namespace ROOT::Experimental;
 namespace REX = ROOT::Experimental;
 
 /**
- * \defgroup REve Event display with ROOT7
+ * \defgroup REve Event display (REve)
+ * \ingroup Graphics
  * \brief Modern version of "Event display" using ROOT7
  */
 

hist/doc/Hist.md

@@ -1,4 +1,4 @@
-\defgroup Hist Histogram Library
+\defgroup Hist Histograms
 \brief A general description of the  Histogram library is documented in the class TH1.
 
 ROOT supports the following histogram types:

io/io/doc/index.md

@@ -1,4 +1,4 @@
-\defgroup IO Input/Output Library
+\defgroup IO I/O
 
 The library collecting the ROOT classes dedicated to data input and output.
 

tree/dataframe/inc/ROOT/RDataFrame.hxx

@@ -9,7 +9,7 @@
  *************************************************************************/
 
 /**
-  \defgroup dataframe Dataframe
+  \defgroup dataframe RDataFrame
 ROOT's RDataFrame allows to analyse data stored in TTrees with a high level interface.
 */
 

tree/ntuple/doc/README.md

@@ -1,4 +1,4 @@
-\defgroup NTuple RNTuple-related classes
+\defgroup NTuple RNTuple
 \brief Classes designed for columnar data storage in modern ROOT
 
 # RNTuple Introduction

tree/tree/src/TTree.cxx

@@ -9,7 +9,7 @@
  * For the list of contributors see $ROOTSYS/README/CREDITS.             *
  *************************************************************************/
 /**
-  \defgroup tree Tree Library
+  \defgroup tree TTree
 
   RNTuple is the modern way of storing columnar datasets: please consider to use it
   before starting new projects based on TTree and related classes.

tree/treeplayer/src/TTreePlayer.cxx

@@ -10,7 +10,8 @@
  *************************************************************************/
 
 /**
- * \defgroup treeplayer TreePlayer Library
+ * \defgroup treeplayer TTreePlayer
+ * \ingroup tree
  * \brief It contains utilities to plot data stored in a TTree.
  * \note See also Tree package documentation
  * \note See also Chapter about Trees and Selectors in the Users Guide