Generate UUID for each track (necessary for synchronization).

Fixes #294.

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

@@ -0,0 +1,23 @@
+package de.dennisguse.opentracks.util;
+
+import androidx.annotation.NonNull;
+
+import java.nio.ByteBuffer;
+import java.util.UUID;
+
+public class UUIDUtils {
+
+    public static UUID fromBytes(byte[] bytes) {
+        ByteBuffer byteBuffer = ByteBuffer.wrap(bytes);
+        long mostSignificant = byteBuffer.getLong();
+        long lestSignificant = byteBuffer.getLong();
+        return new UUID(mostSignificant, lestSignificant);
+    }
+
+    public static byte[] toBytes(@NonNull UUID uuid) {
+        ByteBuffer byteBuffer = ByteBuffer.allocate(16);
+        byteBuffer.putLong(uuid.getMostSignificantBits());
+        byteBuffer.putLong(uuid.getLeastSignificantBits());
+        return byteBuffer.array();
+    }
+}