worked on signal-strength-estimation

add this information to grid nodes
evaluate this information
new test-cases

sensors/radio/model/WiFiModel.h

@@ -0,0 +1,18 @@
+#ifndef WIFIMODEL_H
+#define WIFIMODEL_H
+
+#include "../LocatedAccessPoint.h"
+
+/**
+ * interface for signal-strength prediction models
+ */
+class WiFiModel {
+
+public:
+
+	/** get the given access-point's RSSI at the provided location */
+	virtual float getRSSI(const LocatedAccessPoint& ap, const Point3 p) = 0;
+
+};
+
+#endif // WIFIMODEL_H