java/pulsensor: Changed to C++ types and added callback functionality for Java

Signed-off-by: Andrei Vasiliu <andrei.vasiliu@intel.com>
Signed-off-by: Mihai Tudor Panu <mihai.tudor.panu@intel.com>

src/pulsensor/Callback.h

@@ -0,0 +1,15 @@
+#pragma once
+
+#if defined(SWIGJAVA) || defined(JAVACALLBACK)
+class Callback
+{
+  public:
+    virtual ~Callback()
+    {
+    }
+    virtual void run(clbk_data arg)
+    { /* empty, overloaded in Java*/
+    }
+};
+
+#endif