Adding the Call class (JavaDoc) description.

Change-Id: If0091135df5cfbf6396ddc20207d039e395cbf58
diff --git a/src/com/android/telecomm/Call.java b/src/com/android/telecomm/Call.java
index 3511b7e..a969158 100644
--- a/src/com/android/telecomm/Call.java
+++ b/src/com/android/telecomm/Call.java
@@ -18,6 +18,11 @@
 
 import java.util.Date;
 
+/**
+ *  Encapsulates all aspects of a given phone call throughout its lifecycle, starting
+ *  from the time the call intent was received by Telecomm (vs. the time the call was
+ *  connected etc).
+ */
 final class Call {
 
     /** The handle with which to establish this call. */