Add string based constructors for UPM sensors

Signed-off-by: Mihai Stefanescu <mihai.stefanescu@rinftech.com>
Signed-off-by: Stefan Andritoiu <stefan.andritoiu@gmail.com>

examples/c++/buzzer-initio.cxx

@@ -0,0 +1,12 @@
+#include <iostream>
+
+#include "buzzer.hpp"
+#include "buzzer_tones.h"
+#include "upm_utilities.h"
+
+int
+main(int argc, char** argv)
+{
+  upm::Buzzer buzzer("p:33,vol:1.0");
+  return 0;
+}