Documentation: Flatter hierarchy in SensorActorUnits

etc/doxygen/pages/SensorActorUnits.dox

 /**
-  \defgroup RobotAPI-SensorActorUnits RobotAPI Sensor-Actor Units
+  \defgroup RobotAPI-SensorActorUnits Sensor-Actor Unit
   \ingroup RobotAPI-Components
 
     * @brief Sensor-Actor Units are Armarx \ref armarx::Component "Components" that communicate usually directly with their
@@ -12,17 +12,17 @@
   @li Publish sensor data through Ice topics @see \ref RobotAPI-SensorActorUnits-observers, \ref Observers
 
 
-  \defgroup RobotAPI-SensorActorUnits-simulation Sensor-Actor Units Simulation Implementations
-  \ingroup RobotAPI-SensorActorUnits
+  \defgroup RobotAPI-SensorActorUnits-simulation Sensor-Actor Unit Simulations
+  \ingroup RobotAPI-Components
   Basic simulation implementations of the interfaces that do not consider any physical laws.
 
-  \defgroup RobotAPI-SensorActorUnits-observers Sensor-Actor Units Observers
-  \ingroup RobotAPI-SensorActorUnits
+  \defgroup RobotAPI-SensorActorUnits-observers Sensor-Actor Unit Observers
+  \ingroup RobotAPI-Components
   Almost any Sensor-Actor Unit has an observer, that observes the sensor value of this unit and
   provides datafields for the sensor data. All unit observers implement the \ref armarx::Observer interface.
 
-  \defgroup RobotAPI-SensorActorUnits-util Sensor-Actor Units Utility
-  \ingroup RobotAPI-SensorActorUnits
+  \defgroup RobotAPI-SensorActorUnits-util Utilities
+  \ingroup RobotAPI-Components
   Utility and helper classes associated with Sensor-Actor Units.
  */