doxygen: add groups for all modules

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

src/lsm303/lsm303.h

@@ -60,6 +60,11 @@ namespace upm {
 #define Z 1
 #define Y 2
 
+/**
+ * @brief LSM303 accelerometer/compass library
+ * @defgroup lsm303 libupm-lsm303
+ */
+
 /**
  * @brief C++ API for LSM303
  *
@@ -69,6 +74,7 @@ namespace upm {
  * module that is used over i2c. The magnometer and acceleromter are accessed
  * at two seperate i2c addresses.
  *
+ * @ingroup lsm303
  * @snippet lsm303.cxx Interesting
  * @image html lsm303.jpeg
  */