Added initial interfaces and some sensors implementing them

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

src/moisture/moisture.cxx

@@ -46,3 +46,8 @@ int Moisture::value()
 {
   return mraa_aio_read(m_aio);
 }
+
+int Moisture::getMoisture()
+{
+  return value();
+}

src/moisture/moisture.hpp

@@ -25,6 +25,7 @@
 
 #include <string>
 #include <mraa/aio.h>
+#include <interfaces/iMoisture.hpp>
 
 namespace upm {
   /**
@@ -55,7 +56,7 @@ namespace upm {
    * @image html moisture.jpg
    * @snippet moisture.cxx Interesting
    */
-  class Moisture {
+  class Moisture : virtual public iMoisture {
   public:
     /**
      * Analog moisture sensor constructor
@@ -74,6 +75,13 @@ namespace upm {
      */
     int value();
 
+    /**
+     * Gets the moisture value from the sensor
+     *
+     * @return Moisture reading
+     */
+    virtual int getMoisture();
+
   private:
     mraa_aio_context m_aio;
   };