Bluetooth LE: implemented cycling cadence and speed sensors.

Cadence is working while speed still requires the wheel size.

src/main/java/de/dennisguse/opentracks/util/UintUtils.java

@@ -0,0 +1,30 @@
+package de.dennisguse.opentracks.util;
+
+public class UintUtils {
+
+    public static int UINT16_MAX = 0xFFFF;
+    public static long UINT32_MAX = 0xFFFFFFFFL;
+
+    private UintUtils() {
+    }
+
+    /**
+     * Computes a - b for UINT with overflow (b < a).
+     *
+     * @return diff or -1 (invalid)
+     */
+    public static long diff(long a, long b, final long UINT_MAX) {
+        if (a < 0 || b < 0) {
+            return -1;
+        }
+        if (a > UINT_MAX && b > UINT_MAX) {
+            return -1;
+        }
+
+        if (a >= b) {
+            return a - b;
+        }
+
+        return (UINT_MAX - b) + a;
+    }
+}