Add a Bluetooth-based transport to obd2_lib

Test: manual testing on a Nexus phone
Change-Id: Ia4c4605fa22dca22e18fbdef3b29e3effa98919e
diff --git a/obd2-lib/src/com/android/car/obd2/Obd2Connection.java b/obd2-lib/src/com/android/car/obd2/Obd2Connection.java
index 62b070a..bfdb9c0 100644
--- a/obd2-lib/src/com/android/car/obd2/Obd2Connection.java
+++ b/obd2-lib/src/com/android/car/obd2/Obd2Connection.java
@@ -36,6 +36,8 @@
 
         boolean reconnect();
 
+        boolean isConnected();
+
         InputStream getInputStream();
 
         OutputStream getOutputStream();