snippet: Updated all snippet tags

Ensure all src C++ headers which have corresponding C++ examples have
doxygen tags which point to those examples.  Some were missing, some
were invalid, some needed to be updated to match the new example names.

Signed-off-by: Noel Eck <noel.eck@intel.com>

src/sensortemplate/sensortemplate.hpp

@@ -59,7 +59,7 @@ namespace upm
  * board-specifics, testing, etc...
  *
  * @image html sensortemplate.png
- * @snippet <example-name.cxx> Interesting
+ * @snippet sensortemplate.cxx Interesting
  */
 
 class SensorTemplate