doxygen: add groups for all modules

Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>

src/ecs1030/ecs1030.h

@@ -41,9 +41,15 @@ namespace upm {
 #define TRUE               HIGH
 #define FALSE              LOW
 
+/**
+ * @brief ECS1030 electricity sensor library
+ * @defgroup ecs1030 libupm-ecs1030
+ */
+
 /**
  * @brief C++ API for ECS1030 (electricity sensor)
  *
+ * @ingroup ecs1030
  * @snippet ecs1030.cxx Interesting
  */